


Hotboxing

by Gilded_Pleasure



Category: Undertale (Video Game)
Genre: 'Everyone Is Trans' is the new 'Everyone Is Gay, At Least One(1) Cock Probably, But Also Serious Feelings!, Canon Goblin Sans, Come Marking, Come play, Constantly Emitting Slime, Cuddle Kink, Enthusiastic Consent, Everyone is Trans, Exotic Frottage of the Third Kind, Fluffersmutter and FoxyBox Sanswich, Gay Monsterfucking For Thoughtful Adults, Heavy Petting, Humor, Inexperienced Mettaton, Magic Robot Jizz, More PUNs than Your BODy hAs Room For, Offscreen Established Nonexclusive Sansby, Oral S...omething, Other, Overstimulation, Please Know the way I Write Soul Sex is InTeNSE, Porn with Feelings, Praise Kink, Rarepair, Sensitive bones, Sex Acts I Made Up, Sex Is Fun, Sexy Rectangle Action, Soul Sex, Soul Touching, There's a COVER now, This work is officially my precious unloved ugly baby, Time Fuckery, USDA Extra Fancy Hot Corny Lounge Fucking, Witty Banter, Worldbuilding, continuum mechanics, finely aged niche emotions decanted at last, handjobs, mettasans, monster biology is very different, monster concepts of sex and gender, older characters with less sexual experience is Gay Culture, thanks for coming, they are also gay, weird monster sex
Language: English
Status: Completed
Published: 2019-06-09
Updated: 2019-09-22
Packaged: 2020-04-23 16:01:11
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 4
Words: 27,997
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19154314
Author URL: https://archiveofourown.org/users/Gilded_Pleasure/pseuds/Gilded_Pleasure
Summary: It’s finally here: The METTASANS fic literally NO ONE asked for!!Time inside the barrier passes so slowly, it doesn’t feel like it’s going anywhere. When an hour can last for days, a HoPeless situation can turn terminal without entertainment. Monsters and Fuckers, rejoice & bring a friend, because it’s about to Get Hot in Hotland!Sans the Skeleton decides to help Mettaton get his little “nightclub” idea off the ground, and maybe stave off his own existential fatigue with some bad laughs, good food, and nice friends. Mettaton’s the new Sexy Rectangle on the scene, hoping this box of bolts he and Pervy Alphys came up with holds up long enough for him to take his Spare Parts for a test run……and he’s heard a certain skeleton is Good With His Hands.They might be pretty different, but they both agree on one thing: you have to find a way to kill time before the time kills you.





	1. Mystery Box

**Author's Note:**

> Completely Unnecessary Science Facts:  
> -time is passing more slowly inside the barrier due to gravitational time dilation (https://users.sussex.ac.uk/~waa22/relativity/What_is_gravitational_time_dilation.html), but at a totally unpredictable rate due unequal mass increase  
> -magic and souls obey the laws of continuum mechanics rather than particle physics (https://arxiv.org/pdf/1405.4728.pdf)  
> -some monsters have genitalia and some don’t; all have souls and magic, and can read emotion/intention by ‘tasting’ each others’ magic  
> -Sans’s mandible is fused on the right side and he can barely open his mouth; he has unique biology and enhanced spatial awareness  
> -Mettaton’s body is relatively new and he’s shy for ghost reasons; Alphys is a legendary pervert and Sans’s secret coworker/best friend; Sans has a reputation for being ‘good with his hands’, but spent the majority of his adulthood uninterested in ‘real’ intimacy (soul stuff =‘real’ sex to monsters)  
> \- monsters have a very complex (high context) culture, including their sexual taboos due to Time Fuckery; they have no tradition of sexual monogamy

 

[mystery box]

Mettaton’s irritated chirps and buzzes wake Sans up eventually. He considers pretending to still be asleep, but he has to admit to himself he’s almost as bored as the robot spinning his wheel peevishly, waiting for it to become “tonight”. Whenever the hell _that’s_ going to happen.

That’s when the show’s going to start, and he’d already agreed to help get Mettaton’s little place up and off the ground.

Even if it is in Hotland. Technically. It’s also right on the edge of New Home, though distance is kind of relative down here too sometimes, isn’t it.

Whatever.

Sans slides a socket open to watch Alphys’s person-project trying to wear a hole in the floor.

“that a figure eight?” Sans sighs pathetically, staring at the ceiling. “maybe we should put this show on ice.”

Mettaton rolls to a stop and makes the beepyboopy noise that passes for a sigh. “How can you stand wearing that sweater in this heat?” he buzzes peevishly.

“mm. kinda like that part,” Sans admits. “s’nice n toasty.”

“You only say that because you live in the starforsaken tundra.”

“guess ‘m used ta being _snowed in_ ,” Sans grins. “what’s got your bolts in a bother?”

The sigh again.

“Are you _sure_ you can’t do anything about this, darling?”

Sans’s other socket opens, but only so he can narrow them both at the steel box housing whatever the heck Mettaton is. Sans doesn’t know, and honestly doesn’t care. Mettaton seems to like that about him, so they get along fine. Sure, he knows where Sans works, and the reason he knows Mettaton is through Alphys, but it’s not like he wants that to get around. If people knew he worked on the Core, he’d never hear the fucking end of questions just like this one.

But no one’s here right now to eavesdrop, and Sans would know if there was anyone lurking outside, too. Sans is lying on the floor in the dim interior of Mettaton’s new “nightclub”, which is basically an oversize shack leaned up against one of the uneven protrusions Hotland’s full of, especially where it starts to become not-Hotland. There are five rickety tables with at least three chairs apiece in here, which is kind of an accomplishment considering they probably had to be hauled out here to the middle of nowhere (ha) the hard way. Sans certainly didn’t help.

There’s an equally rickety stage up at the front with a rigged curtain that can be drawn up and down with a pull cord. Shabby but effective, and totally abandoned until it gets dark, which is when Mettaton had told people to start showing up. Whenever _that_ decides to happen. The thought makes Sans sigh as he checks outside briefly.

Nothing but metaphorical tumbleweeds and the relentless light programmed to shine until the fake nighttime the Core provides. The fact that neither fake day nor fake night seem inclined to obey the laws of physics, conservation, linear time, personal convenience, relativity or spacetime no matter how many corrective algorithms Sans punches into the interface is exactly what Mettaton’s complaining about.

“you really think i’d be waiting this out if i didn’t have to?” he asks mildly.

“Your priorities have a tendency to be mysterious,” he points out, and Sans has to admit privately that that’s both fair enough and also satisfying to hear.

“you nervous?” Sans smiles gently.

Mettaton had asked Sans if he would let people know he’s doing one of his “shows” to start things off with a bang, and Mettaton plans to come out between sets as a kind of host. He’d said it was going to be a “variety show”; Sans had objected that one act with a host doesn’t sound like much variety to him. Mettaton had patiently explained that it has to do with there being music, comedy, Mettaton’s juggling, and whatever the hell that other shit Sans does is called, so he’d shrugged and let it go.

“Of course not,” Mettaton buzzes evenly. There’s an extended moment of silence. “I’m a professional showman, after all.”

Sans just smiles gently.

“A little,” Mettaton adds after a minute. “I’m sure there’s something you’d rather be doing than this. I...understand if you...need to...”

Sans winks outrageously, makes an unambiguously lewd gesture. “always have something else i’d rather be doing, but i said i’d be here, an’ here i am.”

“Save it for the stage,” Mettaton beeps, arms crossed aloofly.

Sans rolls onto his side, giggling wickedly. “suit yourself. jus’ looking to pass the time.” He’s teasing him, but Mettaton gets still, and when he does that Sans can’t tell what’s going on inside that midsize steel rectangle at all.

It’s exciting.

Maybe even a little...intriguing.

Huh. Maybe he’s not _entirely_ teasing after all.

“you got something on your mind?” Sans asks quietly, his sharp grin softening. “jus’ us chickens. wanna ask me about something, maybe?” His questions are definitely leading, but where they lead depends entirely on the mystery box over there.

Sans rolls onto his front, lies his skull down sideways on his crossed arms to fix his sights on Mettaton. He kicks his feet up idly in the air, does a little crisscross to draw attention to his socks.

It’s a real nice pair, matching powder blue with white eyelet lace. He saved his best for the show, considering the stage is raised and everyone’s going to get a good eyeful of these babies. He’d paid Bratty 15G for them, still in the package even though they were soaked with muddy water inside. A day or two pinned down under a rock in the river and they’re good as new, or close enough for sans-the-skeleton, infamous sock connoisseur. The rock had asked for another 3G, but returned it when Sans had come back for the socks.

Rocks tend to be pretty solid dudes.

Heh.

“I do have some...recent upgrades that have been...slightly challenging to figure out,” Mettaton says after a long, long time. That’s okay, Sans is nothing if not willing to wait for it. Let him decide where he wants this to go; after all, they’ve got nothing but time to kill, and they better so it doesn’t kill them first. Sans nips that train of thought off before it can send him somewhere less pleasant than than path he’s on right now; it’s just starting to get interesting in here, and the last thing he needs is to end up under the table at Grillby’s bawling all over Lola.

Sans hums in acknowledgment, lets his smile gets even more suggestive. Crosses his ankles delicately over his skeleton butt and stretches his arms out in front so Mettaton can see his hands. “you could say ’m mechanically inclined. want me to take a look under the hood, see if it’s up ta snuff?”

Mettaton’s display surface goes through several different changes in colors and patterns. Sans has no clue what that could mean, so he just waits for a response he can actually parse, although he certainly commits them to memory just in case. He wheels a little closer too, and that has to be a good sign, right?

“That is...certainly forward.”

Sans’s smile slips a bit, and he rolls over to sit with his legs tented up, elbows on his knees to keep the slick material of his shorts in place. He lets his hands dangle between his knees casually, tries to keep his voice even, but some sharpness creeps in despite him.

“lotta people _talk_ , but there’s only one way to find out what’s what.”

Mettaton comes closer again, which isn’t the reaction Sans was expecting. Okay, yeah, this is pretty fun.

“I wasn’t complaining,” he buzzes, then keeps rolling forward. “I’m...curious. About how those upgrades I mentioned perform...on the road. With someone mechanically inclined test driving.”

Sans starts to smile again and moves his hands apart invitingly; Mettaton apparently noticed Sans has a penchant for reading car magazines he keeps in his phone when he’s too bored to sleep. Making a point to mention it… he’s interested for _real_ , isn’t he? Maybe he has been for a while; Sans had suspected, but it’s nice to have it confirmed. Then his grin drops as something important occurs to him.

“born after?” he asks quickly.

Mettaton gives him a color pattern he recognizes as haughty and impatient. “New Home; before _Alphys_ ,” he answers peevishly. That’s perfectly fine, then. He’s no spring chicken either. “You?”

Sans laughs outright. “snowdin. before papyrus.”

“That’s not exactly-”

“before craig, too” he amends before Mettaton can finish that sentence.

“I don’t know what _that_ look was for,” Mettaton beeps. “I don’t know anyone named Papyrus.”

Sans shakes his head at himself and laughs. He always thinks someone’s going to have something rude to say about his rude brother, but the fact is Mettaton’s just high strung and unpredictable. Kind of bitchy, always has a comeback. A little like Grillby that way. Sans grins lazily, a single socket slipping shut as the realization gives him a little thrill deep inside: apparently Sans has a _type_. Who knew.

He’s hesitating, which is fine by Sans. He’s always glad to let the moment linger, and if he takes what Sans is offering, he wants him to be sure.

“I truly don’t mean to assume,” Mettaton buzzes. “You understand that I have-”

“yeah,” Sans interrupts low and confident, reassuring before the robot can lather himself up too much. “i know what to do.” He puts his arms up on his knees, beckons invitingly. “want me to prove it?”

And that’s another fun thing about Mettaton. No face, very few tells. Not malevolent or anything; just potentially full of surprises to fill up the time with, shake things up a little. Introduce some _chaos_. Sans lets that bright little spark of temptation he feels in his soul light up the lazy gaze he fixes on the robot inching toward him, dangles a promise of something good, something unexpected, something worth coming the rest of the way across the room to investigate.

Sans can wait all day; he already has, and will continue. For as long as it takes.

Mettaton wheels over slowly; Sans thinks it’s shyness, not reluctance. When he gets close enough, Sans brings his hands in, lets them slide across metal with a soft rasp. They’re both real hardbodies, aren’t they. Heh. Mettaton’s a _lot_ sturdier than he is, though. It’s even more obvious when they’re so close, touching like this.

“Do you want me to touch you too?” Mettaton’s voice doesn’t have much volume control on it; no big deal. They’re all alone, so there’s no one to hear if they wanna get loud about it. Not that Mettaton has much choice.

“mm.” Sans sets his frontal bone on the metal box with a clink-clack. “got a question for you first. you ever check me?”

“I...” Mettaton hesitates; Sans just waits. No real reason he ever would have, is there. “No.”

“go head and do that.”

He waits some more.

“I take it that’s a no?” Mettaton says eventually. Sans knows what he sees; not what it says, of course. But the stats.

“kinda the opposite, actually,” he smiles slow and soft, rubs his frontal bone across. “oh, uh. that ok? you feel it?”

“Of course,” Mettaton says flippantly; something else underneath. Sans can’t hear it, but he can guess. “What do you mean by ‘the opposite’?”

“means i _want_ you to touch me, as long as that’s what you wanna do too. jus’ gotta be careful, cause ’m a delicate lil skeleton. do it nice n easy, specially between the bones, okay?”

He makes a mechanical noise that Sans realizes is a kind of snort. Functions as one, anyhow.

“it’s fine to laugh s’long’s you know ‘m not kidding,” he adds, and Mettaton’s hands stop on his hips.

“I know you’re not. I’m listening, so let me know if you don’t like anything. Let me… let me know if you _do_ , too.” He’s not young, but he’s inexperienced. Sans feels a pleasantly warm glow somewhere private; could be Mettaton’s like him. Late bloomer, maybe.

Wow. This mystery box sure is full of surprises, and so far they’re all the good kind.

“mm,” Sans says, relaxing the rest of the way and letting his sockets close as the hands on his hips start caressing his iliac crests through his shorts. “same here. you decide you want me to get bold with you, jus’ tell me where, or show me when you’re ready.”

“I will,” Mettaton adds shortly, then makes a little beep when Sans runs his hard fingertips over the place where his long, slinky arm emerges from his box-body.

“good?” Sans asks, sockets still shut.

“Apparently,” he buzz-drawls, and Sans huffs in amusement. Then he touches there again, puts a little more flourish on it.

They touch each other slow and careful, getting a sense for what good responses are, asking and answering with increasing comfort. The beeps are good, crackles are not as good. Sans explains the shivers, and laughs a little when Mettaton comments on the mildly increased temperature in his face and breath. Would ya look at him. Getting all hot and bothered in Hotland.

“You have a wonderful laugh,” Mettaton says unexpectedly. “No wonder people pay to hear it.” Sans chokes off a noise that might have been embarrassing even for him. Hoo boy.

“uh, thanks,” he manages, surreptitiously wiping his forehead on his shoulder even though it doesn’t need it. Not sure why he thought it did. He’s glad his sockets are still shut so his eyes don’t flicker when Mettaton asks him a follow-up question.

“Can I touch these?” Mettaton’s fingers indicate his vertebrae with a light touch.

Sans opens his sockets, focuses in on Mettaton’s display with a gentle caress as he considers.

“go for it,” Sans replies softly, then shivers in delight when he realizes Mettaton’s display is also touch-sensitive, and that he can make little squares light up with bursts of colors in response to San's fingers. “ohhh, that’s fun. you like it?”

“Of course it is, darling. And yes,” Mettaton says, then Sans grunts softly when gloved fingers tease along his spinal processes. Mettaton stops short, waits.

“yeah, keep on like you been,” he encourages, enjoying the play of touch and response on the display. “you can rub in between there if you want, too. that’s real good for me.” He does, and it is.

“The catch for the panel is underneath. In front of the wheel,” Mettaton buzzes eventually. Sans opens and shuts his sockets for a second, finds it easily once he remembers oh yeah, that was the idea here, wasn’t it. He smiles gently at himself; Mettaton’s good enough with his hands to be pretty distracting.

“you’re good with your hands,” he says quietly aloud as his phalanges explore Mettaton’s boxy undercarriage, and he makes a tiny series of metallic chirps. “can’t complain bout the sweet talk, either. mm,” Sans adds enthusiastically, determined to give as good as he gets. A distal phalanx finds an edge.

“Pull there, and it’ll...come out,” he explains, voice almost...fuzzy?

He does, and it does.

“that’s real nice,” Sans says softly, admiring. “you want to me to touch it like i said before?”

A thumbs up crosses Mettaton’s display, making Sans grin. “you got it,” he murmurs, enjoying the continued thick-blunt play of gloved robot fingers at the tight magic that holds his spine together. Sans’s touch isn’t tentative, but it is gentle and explorative. He’s not really getting much feedback, though.

“how do you like it?” he asks softly without doing anything repetitive or firm. Mettaton seems at a loss for words. “you tried it out yourself?”

“I did. Once or twice.”

“k. put your hand on mine, show me how you did it.”

Sans makes him pause almost right away.

“seems a little rough,” he frowns in confusion. “you feel it, right?”

“Of course. It’s lubricated with my magic when I...want it to be touched. That’s how it’s designed.”

Sans hums thoughtfully.

“did alphie show you those human animations?”

“I… didn’t need her to see them. I already watched them on my own.”

Sans thinks about what kind of ideas he might have gotten from them. He’s pretty sure most of that stuff’s physically impossible, and all of it is nothing a monster would like. Nothing he could _imagine_ one liking, anyways.

“want me to try it how some people like if they got something sorta like this?”

“Well, yes. That’s why I _asked_ you, darling.”

Sans grins appreciatively, then pulls Mettaton closer with his free arm until he’s pretty much wedged between his tented up legs. He sets his forehead against the steel box of his body, gives it a little nudge.

“’m glad you asked me,” Sans murmurs, fingers forming a loose circle, then tightening experimentally. A faint beep; the good noise. That’s encouraging, so he loosens again and tries sliding a little, then adds a squeeze at the end. More good noises happen, so he feels a bit more confident that he’s got an idea of what will work here.

“you working up to something? get a little shiver from it?” Some do, some don’t.

“I’m not sure,” Mettaton replies with a few tonal breaks in his metallic voice. “I didn’t get that far on my own.”

“s’okay,” Sans replies, tries out a gentle tug to great effect. “we can find out if you want, or jus’ let me know when you want me to stop.”

Mettaton’s slinky arms tighten around him; it makes Sans’s breath shaky with delight.

“that’s real good,” he whispers, gives a shiver of his own. “will you hold on to me like that while i do it?”

Mettaton’s fingers trace bones idly. “Of course, beautiful. You’re so gentle,” he adds; his voice doesn’t really have the usual sort of emotional nuances, so it’s hard to say if that’s good or not. “I like it,” he adds before Sans can ask. It makes him smile, and he tries going a little faster although he keeps the bones of his hand loose.

Sans lets his sockets slip shut again as Mettaton holds him close and tight, then moans softly when gloved fingers slide gently over his occipital bone. “there ya go. nothing wrong with taking it easy.” He turns his skull to the side, leans it heavily into the steel box he’s pleasuring to the best of his ability. Which based on cumulative feedback he has reason to believe is considerable.

“that’s it...” he rambles absently, lets out a little mew of pleasure as Mettaton pets his parietal bone and hugs him tight. “does it feel good yet?”

A surprisingly quiet burst of tones greets his question.

“Better than I expected,” Mettaton answers, and Sans makes another soft sound as he gets held and petted even more.

“same here,” Sans whispers, breathing a little faster. “mm.”

Mettaton holds him tight with one arm while his fingers roam lightly along his skull and down his vertebrae, digits massaging unhurried at the magic between them before gliding across his clavicle. He isn’t just hugging him or pawing at him as a byproduct of his own pleasure; he’s actively trying to make Sans feel good, and it’s working. He doesn’t even have a mouth, but he’s using his hands to touch all the places Sans likes, paying attention to how he reacts. He tilts his skull back and leans into the touch when Mettaton caresses his open hand soft over his occipital bone again, makes some more noise, too.

“Is it good down here as well?” Mettaton asks with a questioning touch the tip of a lumbar process where apparently his shirt and hoodie have ridden up a bit.

“go for it,” Sans whispers with an anticipatory little shiver. He grunts softly as he threads those soft-gloved fingers between the processes; again when they slide around the rim where they start to become between. Mettaton’s thumb toys gently around his spine like he’s playing an instrument, fingers sliding up until they touch one of his floating ribs hesitantly, then stop.

Sans tilts his skull back just a little, although he doesn’t know why he keeps looking for a face when there isn’t one. Wow. This robot’s got him ten kinds of flustered, and he’s really not complaining.

“you wanna touch me there?” he whispers, and he can hear the barest tinge of surprise in his own voice. No clue if Mettaton can hear it too. Ohhh, that’s what so oddly exotic about this; Mettaton’s body doesn’t convey intent with his touch. It’s completely unpredictable, like not being able to read the expressions he doesn’t have. His body’s artificial, so it’s not...continuous. It’s nothing like being touched by fire, claws, or tongues, that’s for sure.

“Does that feel good for you?” Mettaton asks curiously.

Sans lets the sincere smile burbling up inside him take his features; he can feel his eyes expanding. “only one way ta find out,” he sighs. “gotta be real easy though, k?”

“I’m finding myself with a newfound appreciation for taking it easy,” Mettaton replies. Sans’s soft laugh turns into a different noise, might even be a little moan, as a soft gloved fingertip slides across the surface of his bottom-most true rib.

“you got me real excited,” he pants in surprise after another minute or two. Sans changes the way he touches Mettaton, goes back to light and coaxing, drawing it out. “you, uh. wanna put it in there?” He doesn’t answer, but a fingertip teases very lightly into the space between his ribs, rather close to where it joins his spine. Sans gasps a little, and the fingertip hesitates.

“it’s good,” he exhales, then shudders hard when it slips further between, rubs a little. His shaking doesn’t seem to throw this robot off his game at all either; he just corrects for it, and then next time it happens, he lets Sans quiver around his finger, letting Sans stimulate himself with the movements of his own arousal. Well. That’s uh. Yeah. It _really_ gets his motor going, and he adds that enthusiasm back into what he’s doing with his hands.

“s’okay if you don’t wanna take it there, but…” Sans sighs as a fingertip brushes the inside surface of his rib delicately. Perfectly. He’s not in a hurry. “…was jus’ wondering.” He shivers hard when that same finger moves in a little more, grunts softly as it slides around toward the front, close to his sternum. Oh, that’s _bold_. “…if i could have a taste?” he finishes with a sigh.

Another, louder burst of tones greet his request. Sans hears his own rounded exhale of pleasure; Mettaton finger-bangs him with casual care while he thinks about it.

“Go ahead,” he says eventually, scratch-buzz voice managing to sound tight.

“mmmm,” Sans hums in anticipation, then switches hands so smoothly he’s not sure Mettaton even notices. He definitely doesn't stop holding him, and that just adds to his excitement. He ducks his head and manages to worry a magic-dampened distal phalanx through the widest point between his teeth, tilts his skull back and moans soft and clear when the taste hits.

Mettaton really likes what he’s doing, and he thinks he might get that little shiver Sans was talking about before. He definitely wants to find out if it’s going to happen or not at the very least. Not only that, he’s loving touching Sans just as much as being touched _by_ him, and that’s an unexpected level of pleasure added on to the rest, wow. No wonder he’s good at it. His magic’s light and fluffy, barely-there and refreshingly astringent. It spreads apart into Sans’s mouth like watercolor, and leaves a clean aftertaste like pressed leaves.

_Nice._

“’m good for it til you’re ready to call it,” Sans whispers, then feels his own magic well up in his sockets in response. He’s surprised. He wasn’t expecting to spend at all, didn’t realize he could from just tasting. He switches hands again, surreptitiously tugs his shirt down between his legs where apparently his magic decided to offer itself up somewhere else too, soaking into his shorts a little. They’re not even touching with intent towards souls; this is only bodies...well, now it’s officially foreplay, heh. Sans puts his arm back around Mettaton and pulls him close and tight, thinking about how flattered he is that he came to him for this. It makes him feel good that Mettaton wants to feel this way with him so near, to let Sans help him figure out how he likes to be touched.

For Sans it’s exciting to pleasure someone just like it always is, but there’s actually a little more here, too. He didn’t expect that; this is better than expected for _both_ of them, he thinks. So when Mettaton finally gets brave enough to ask for a taste in return, he tilts his face up and offers up his streaming sockets to gloved fingertips. He wasn’t expecting him to press it to the tip of where Sans’s hand works rhythmically, but once he does there’s another burst of sound almost like static. Apparently he can taste it there.

“You’re so sweet,” Mettaton manages, voice a collection of disparate tones now as if his usual scratch-buzz is deconstructing itself into chaos. “I...think it’s going to happen,” he rushes out, and Sans moans again when slinky steel arms squeeze him hard.

Then he starts in surprise. Welp. That’s definitely _happening…_ all over his shirt. Good one, Al.

“Ohhhhhh my goodness,” Mettaton says full-voiced, stroking Sans’s back in rapid encouragement, “Ohhhh dear, _darling_ , I’m….”

He stops short, then resumes slowly.

“I _do_ apologize,” he finishes sheepishly.

Sans shakes his head, hugs him back tight and ignores the mess.

“probably shoulda seen that comin’” he quips wryly. “that’s on me.” Literally. Mettaton makes his snort noise. “s’not like i didn’t know _alphie_ made it.” He pulls back enough for Mettaton to see his grin. “you’ve met her. ’m guessing you didn’t know that was gonna happen either?”

“Not exactly,” Mettaton replies primly.

Sans chuckles, shakes his skull. “she got us both with one shot, huh?”

“I’ll...have to have a discussion with her regarding the finer points of homage versus imitation for its own sake,” Mettaton lobs back, and this time they chuckle together. Alphys and her pervy human animations. It’s always more fun to share a joke than feel embarrassed.

“You’re a lot funnier offstage,” Mettaton observes wryly.

“then i hope you appreciate how hard i gotta work to keep my reputation,” he shoots right back with a wink. All entendres intended, as usual. Then Sans glances out the window; of course it’s finally starting to dim _now_.

“i gotta go get changed, but i’ll be right back. you all good?” Sans squints, uses the hem of his already-soaked shirt to carefully wipe a stain off stainless steel. There we go, all polished and bright. Ready for showtime.

“I’m better than good,” Mettaton informs him, voice steady and confident as far as he can tell. “I’m _ready_.”

“heh heh heh… yeah.” Sans is still sitting there on his ass, thinking and looking. If he’s this good at touching his body, makes him wonder how good he might be at touching other stuff, too. Mettaton gets still again, seems nervous. Sans gives him a big, broad smile, sockets long and oval with satisfaction.

“jus’ thought i’d mention,” he says in his always-casual deep rumble. “that was a lotta fun. if you’re interested in getting closer sometime, i might be up for that.”

“Oh...” Mettaton says, “Oh, I’m, I...”

Sans shakes his head with an impish grin, then heaves himself to his feet with a grunt. “jus’ puttin it out there. for now we got a show to do, right?”

“Right,” he replies. It almost sounds soft.

Sans winks, and disappears into a doorway.

“be right back.”

The words appear, but he’s already gone.

 


	2. Fabulous Prizes

**Summary for the Chapter:**

> Oral S...omething

[fabulous prizes]

 

“Congratulations on the worst jokes I have _ever_ heard, darling,” Mettaton buzzes cheerfully at Sans, who’s taking a “nap” on the couch in the “green room” Mettaton’s set up in the latest version of his “nightclub”.

 _Everything_ here deserves scare quotes around it in Sans’s opinion.

Not that he’s inclined to share those very often, and not that he excludes himself from that particular roundup.

Sans cracks a socket, the white point coalescing inside reluctantly.

“…hm. really? thought i was kinda off my game tonight, ta be honest.”

Sans has been feeling off his game for a while now. Tired, out of sorts. And every time he thinks of doing something about it like following Papyrus around, going to Grillby’s (and maybe inviting Grillby somewhere private for a little tug-and-tickle), or just slinging some illegal ‘dogs at one of his five stands situated in various in the way out-of-the-way spots, it seems like _way_ too much work.

Just thinking about it makes him want to take another nap already. He’s glad to hear his unfortunate mood is not apparent to others, at least. He continues to lie there on his back, staring at the ceiling rather than the chirpy little box wheeling towards him, and uses his clever phalanges to scratch idly at his ribcage through the shirt, arms bent at the wrists like the world’s laziest and boniest t-rex.

“Tell that to the take, _Comic_ Sans.”

Mettaton wheels up to the low table in front of the busted-in couch, opens a panel at the top of his head and pulls out a strongbox that clanks and jingles loudly as it hits the tabletop. When people show up, Mettaton just stands at the door and lets people put the money into a slot in the top of his body; he seems to get a moderate amount of jollies pretending to be a box, or a control panel, or a lamp sometimes.

Sans finds that aspect of Mettaton’s humor extremely appealing, and is honestly what he’d be spending 90% of his time doing if _he_ happened to be shaped like a box.

Doing a whole lot of nothing and letting people stick money in his head. Living the dream.

“...wow,” he agrees after Mettaton dumps the take. He even opens his other socket and turns over on his side to get a more accurate count. “huh. guess ’m gonna pay my tab soon after all.”

“I _told_ you promotion would pay off, despite the...temporal considerations.” Alphys has managed to fine-tune Mettaton’s voice a lot since the first draft. Sans appreciates that he uses his indoor voice backstage now that he has one, although he rarely hears it otherwise.

Sans makes his slide-whistle noise at Mettaton’s pun; the change in display colors lets him know it hadn’t been intentional. Mettaton provides a rimshot anyhow, and Sans laughs, cheered slightly by the extra money and someone else who can appreciate a good sound effect reel.

And can also produce one. It makes him feel less ( ~~anomalous~~ ) weird.

“That sounded suspiciously close to a real laugh.”

“eh. what can i say. ‘m a jobber for a good rimshot.” Sans gives his best leer.

Mettaton just sits there. “Sad to say, if that’s some kind of entendre I don’t get it.”

Sans is disappointed. He’d pawed through Alphie’s collection a while back to see if he could find some good human sex puns, but it appears he’s fallen...short.

“don’t worry bout it. how’s that new battery pack doing?”

“Interesting...you should ask.”

Sans is feeling cheerier by the second.

“why’s that?” he plays along gamely. He has a feeling he knows where this is going.

“Well...I was hoping you might be willing to test out another upgrade.”

“mm. i might be.” Sans pulls out his phone, clops his arm on the table and scoots his half of the take off the edge and into it. Then he makes the herculean effort of sitting upright, although he immediately slides down the couch until he’s slumped so low his shoulders almost touch the butt cushion. The fact that they _don’t_ proves to Mettaton that he’s more than willing; he’s already hot for it. Sans being coy isn’t really all that coy, and Mettaton knows it.

Sans figures what he means by ‘upgrade’ is some kind of new genital attachment. All of those have been arranged on a sliding scale of hilarious to awesome, which amounts to “win” and “win more” as far as Sans is concerned. Mettaton knows Sans is renowned for being down for some clowning around. It really turns his frown upside down, so he grins with casual anticipation and flips the switch on Mettaton’s boxy ass as requested.

He is nevertheless very surprised by the cloud of glitter and Mettaton suddenly being human-shaped and about two and a half feet taller than him. He’s a little glad he’s already sitting down.

“...wow,” he says, craning his neck up at the soft-silicone face grinning at him smugly.

“That’s true,” Mettaton says, then winks a furry-lashed silver eye at him. Even his voice is different when he’s in this form.

“how the weather up there?” he tries, and gets snorted at for his trouble.

“We’re in _Hotland_ ,” Mettaton snickers, then widens his new eyes mockingly. “It’s _hot_.”

“yeah you are,” Sans chuckles, then again when Mettaton gets down on his knees to approach. The fact that he poses his still-slinky arms to make like a little teapot as he waddle-minces forward—still kneeling—just makes it even funnier.

The closer he gets, the more uncanny his appearance becomes. It’s really...very...not _realistic_ , but…

“alphie’s real talented, huh?” Sans says softly. Mettaton’s eyebrow quirks. He doesn’t disagree, but-

“jus’ meant you look real pretty,” Sans clarifies, and Mettaton’s furry black eyelashes flutter becomingly. Sans produces his hands and wiggles his fingers; he strokes soft black hair and touches silvered-silicone skin when Mettaton raises his chin invitingly. Mettaton exhales shakily and lets his eyelids droop a bit as Sans explores his face, shoulders, and torso with curiosity and enjoyment. “feels real pretty too,” Sans quips, then leans back again as Mettaton puts his hands on Sans’s slick black shorts-covered femurs. “you got somethin’ in particular you want me to try out?”

Mettaton looks down, then grins when he meets Sans’s gaze with a freshly practiced smoldering look.

“Can I try some kissing?”

Sans knows his eyes are flickering; he feels it. Can’t really stop looking down reflexively either. Sans has his tells if you manage to find one of his sore spots, and he has a lot more than people are expecting. That’s why he doesn’t let many people close enough to actually find any of them. His face, especially his mouth, is one. He shakes his skull side to side silently, since his reaction already made it obvious he can’t play it off with a joke.

When he looks back up, Mettaton doesn’t seem bothered by his response, but there’s still a crease between his perfect black brows.

“I meant… I hoped you would let me touch you with my mouth instead of my hands?” he clarifies, and Sans feels his eyes flicker again. “It’s fine if you don’t want that.” Oh. Welp, guess he’s an open book at this point. He scratches his vertebrae self-consciously, then pulls his hand back down with a sheepish grin.

“dunno why ‘m surprised you know me like that,” Sans says quietly. “but i am. ‘s usually the other way round.” When he looks up, Mettaton’s lips are parted in a fascinated and moderately aroused expression.

“It’s because I don’t have a face,” he breathes wonderingly. Then he lets out a short little laugh and tilts his head, smiling charmingly. “Well, not usually.” He shrugs with a little giggle (and a wiggle), and his silvery eyes slide to the side and back. “Here, just…look at this.”

Mettaton leans in and sticks his tongue out at him. Sans leans in curiously, then reaches out with a curious phalanx. Mettaton bends forward even more so Sans goes ahead and touches it, then his sockets widen. Ohhh, his _magic’s_ on there. Like with the genitalia.

“...wow.”

Mettaton puts his tongue back, sits back on his heels and grins smugly. “I know. Alphys really does have a way with these things, doesn’t she?”

Sans giggles. “sure does.” He feels his magic do a slow shift in his body, turning itself over in lambent interest. Huh. Apparently this whole mouth idea really does it for him, especially if Mettaton’s not expecting Sans to be able to part his teeth or have lips or anything like that. Sans leans forward and lifts his chin a little, indicates his vertebrae. “you wanna try it here where you touched before?”

Mettaton’s gaze hoods with intent, and Sans feels a shiver clack through his spine lightly. He leans in and wraps his arms around him too (nice), but Sans is still surprised by his own soft moan when Mettaton’s mouth opens on his neck, then again when he pushes his tongue at the spaces between the bones. There’s no heat and Sans can’t really taste his magic this way, but Mettaton already knows that. Both of their bodies are the same ambient temperature as the environment. But what it is, is softness...pressure...movement. _Physicality_. _Still_ no intent through the touch, even with the magic going on there. Whoa. Feels unpredictable, feels… kinda kinky.

Yeah, it’s really doing it for him.

“that okay?” Sans breathes when he realizes his curious little phalanges have decided to go adventuring on the robot’s new torso. The whispered affirmative blows into his body and makes him shiver hard, sends the permeable magic between his bones into a wide, full oscillation. Hoo boy.

“we gotta be real careful like this, huh?” Sans whispers as their touches grow bolder, making them both gasp and wiggle with the novelty and the odd little thrill Sans definitely feels, and he suspects Mettaton does as well. He doesn’t _know_ though, and that’s where the thrill comes in. “you like it?”

“More than I expected,” Mettaton replies, the newly nuanced voice providing a husky tone that makes Sans’s spine clack in response. “That’s becoming a… theme, apparently.” Eventually Sans finds himself leaned back into the couch, Mettaton’s mouth running along his neck like a bone harmonica and his hands fingering his lumbar spine like a flute. He shivers and sighs, feels downright played in the best possible way.

Phalanges creep down the front of Mettaton’s hard casing curiously, wondering if that panel’s still around here somewhere when he’s like this. “you want me to do that thing again?” Sans asks, enjoying the husky tones happening in his own voice now as he tickles as far down the robot’s carapace as he can reach easily.

Mettaton’s taken him up on the offer a handful of times (heh) since the first time; turned him down once or twice, too. Especially memorable had been the afternoon he’d asked Sans to take his shirt off and spent what maybe have been several hours’ worth of their fifteen minute stage break touching his bones. Rubbing and fingering, watching and listening to all the little noises and shivers. This is still the first time Mettaton’s come on to _him_ , though.

“Actually...” Mettaton whispers into his body from the neck of his shirt, breath finding its way down into his ribcage. Feels pretty good when he does that. Soft-gloved fingers toy with his waistband now, stretched tight over his broad ilia where they curve in. “I was wondering if I could see what you look like here?” Sans gets still. “I showed you mine, right?”

“hate to break it to ya, but...nothing cept bones in there,” Sans informs him, confused since it should be obvious.

Mettaton looks amused rather than disappointed or whatever when he pulls back to look at him.

“I would like to _see_ bones, if you want to let me,” he says impishly, shaking his hair a little. “Possibly _touch_ bones…if you, um...wanted me to.”

Sans huffs out a little breath, rasping his thumb distal across his own broad chin as he glances to the side and feels his magic seethe into his face. “welp. who’m i to say no to a face like that,” he rumbles, then grins and shrugs. He leans over, preferring to take off his own shorts thank you very much, and pauses for a moment to fix Mettaton with a look.

“gotta be real easy, ok?” he says, mild and implacable. “it’s, uh. sensitive. like here,” he continues, indicating his ribs with a quick slash of his thumb, “little more, maybe.” He gives him a pointed look up and down. “and you’re kinda huge right now.”

Mettaton reassures him and winks, so Sans pulls his shorts down until they puddle over his slippers.

“like i said,” Sans says with another self-conscious shrug. “nothing but bones.”

“ _Lovely_ bones,” he corrects, making Sans’s magic seethe into his skull and spend lightly across his frontal bone. “You look like a little white butterfly here.” Sans manages to bite back a moan at that; wow. Being a robot must give you a knack for pushing all the right buttons.

He laughs softly at his private joke and rubs Mettaton’s shoulder with appreciation and encouragement. “And the colors in your magic,” Mettaton adds with a toss of his head, sliding a finger in the dip where his femur joins his pelvis and earning a soft little clacking noise from his spine. “ _Very_ complementary.” He adds a wink on that one for gravy, the overclever little fuck. Iridescent blue and yellow on dance along the light-dark magic holding his body together, the conditionally permeable body between his bones. That’s exactly the kind of bullshit Sans loves.

He smiles at Mettaton kneeling between his femurs with a hint of unaccustomed shyness. This reminds him of being naked the first time he showed Grillby his soul, seeing his own body differently as he wonders how it looks to someone else. Feeling like he’s weird-looking at first, then having someone tell him they like looking at him, they like how his body is. Making him feel good about himself instead. Yeah, Sans could do _this_ all day, even the ones that last a week.

“You look beautiful like this, darling,” Mettaton says in his new, more nuanced voice. Then Sans gets distracted quickly, jumping with a tight noise as a soft, gloved thumb glides into his iliac fossa on either side.

“guess ‘m a lot sensitive,” Sans says sheepishly. “little, uh. ticklish, maybe.”

“I see.” Mettaton looks undeterred. “Well, how do you do it?” he asks, apparently not above cribbing from Sans’s playbook.

Sans sighs, glances to the side and back. “…heh. uh, i don’t.” Mettaton frowns and tilts his head, and Sans clarifies. “not with my hands,” he says, watching Mettaton’s glide up and down his femurs. It makes him sigh, sends a wave of pleasure up his spine. “feels too… hard, lotta the time? use a blanket in there...clothes, sometimes. soft things.”

Mettaton spreads his hands out and looks at them with a little frown, then shows them to Sans.

“What if I use the palms?”

“jus’ the outside?” Mettaton nods. “go for it,” Sans agrees, then exhales unevenly as gloved palms slide firmly over his iliac crests. “…yeah,” he encourages softly. “that was a good idea.” His breathing gets tighter as he does the same over the twin outer curves of his obturator foramina, then shivers as one stays there to lift his hips slightly.

The other palm glides with almost comically-careful widespread fingers along his left inferior ramus toward the joint of his pubis, where tight, dense magic gathers light-dark and iridescent like a shadow’s shadow. Mettaton’s leaning in to have a good look at what he’s doing, and he can hardly miss the magic that wells up when the base of his thumb touches the edge of a pubic bone where they join. Even if he had, the shaky noise Sans makes when it does probably could have clued him in.

“Good?” he whispers, so close Sans can feel his breath blow across sensitive bones. He nods. “Can I taste?” Mettaton asks, a glitchy little wobble happening somewhere in the mechanical tones.

“yeah,” he whispers eagerly, rasping his radius along his frontal bone slowly.

Sans hears his own breath go ragged in his skull as Mettaton leans in toward his pubis, and chokes off a whine as he maintains eye contact. For some reason this is seriously doing it for him, and he hasn’t even done it yet. Heh, that’s what she-

When Mettaton’s tongue touches the shed magic beading up in Sans’s pubic symphysis, they’re both a little startled by the deep, soft growl that comes out of him. It’s just soft silicone at ambient room temperature, lubricated with magic he can barely taste in return this way. But it is very decidedly both tasting him and adding another dimension of pleasure to the experience of _being_ tasted that he’s hard pressed to categorize exactly. Sans is panting as Mettaton pulls back.

“Is that okay? I can do it somewhere else if it bothers you.”

“s’not bothering me,” Sans manages. “kinda the opposite.”

Mettaton’s expression goes from concerned to smug in a nanosecond; it’s compelling how expressive his face is this way considering he doesn’t even _have_ a face in his other form.

“any chance you might wanna do that some more?” Sans asks hopefully.

Mettaton tilts his head with another pretty little frown. “Are you sure it doesn’t feel like…?” he trails off; Sans wouldn’t know how to put it either but he knows what he means. After all, Sans is shaped almost as much like a human as Mettaton is right now, and he’s got a suspicion that might be part of why Mettaton’s so...interested. Sans has seen the stuff humans make that ends up in the dump, half of it in Alphys’s impressive collection for her and Mettaton to pore over in their Fan Club or whatever. And it’s not like he doesn’t know plenty of monsters have genitalia right around this spot, too.

Sans just...doesn’t.

“nah,” Sans replies quietly, stroking Mettaton’s soft black hair with idle patience. “what you see is what you get. jus’ sheds out sometimes when i get excited. hell, i can only taste you there a little more than on my bones… but, uh. it feels real nice anyhow.”

Most monsters have a few areas on their bodies especially sensitive to other monsters’ magic: mouths, genitalia, hands, even whole bodies for some, like Grillby. Although everyone’s different, the existence of those extra-receptive places are almost universal, but Sans has far fewer than most. Just the inside of his skull as far as he’s aware. He feels his magic seethe hard into his face; a few drops become not-him just as eagerly as between his legs. “you interested in, uh. _seeing_ what it feels like for me?”

Mettaton can’t blush, but that’s definitely an expression. He looks like he’s saying “oh,” but nothing actually comes out as his mechanical eyes look for something safe to look at. He really wasn’t expecting that kind of offer, apparently.

“s’okay if you don’t wanna,” Sans adds easily, since he means it. “i already like what we’re doing a lot, so you take your time thinkin bout it, k?” Mettaton nods, and Sans rolls his skull along the cushion as his sockets slide half-mast, gives a pleased little hum. “could i have a taste, maybe?” he asks in a whisper.

Gloved fingers trail up and find phalanges, bring a distal to soft-silvered silicone lips. Sans makes a little noise as Mettaton coats his fingertip with his magic; Mettaton exhales tightly when Sans pushes the fingertip slightly into his eye socket, curls in to rasp it gently on the inside of his skull rather than trying to pry his teeth apart right now. He tilts his skull back as his sockets close, sighs deep and shivers when the taste hits, sliding his hands down to stroke Mettaton’s encouragingly.

Enjoyment, curiosity, peaky little thrills of interest and gratification, all of it laced through with that wispy shyness. He presses his skull back into the cushion and finds himself making a soft little moan, squeezing the robot’s hands in his. That tight-faint bloom of watercolor tastes just as good this way, feels a little more like seeing than tasting but it’s...oh. Mettaton’s talking, so he opens his sockets again.

“Can I taste too while I’m thinking about it?” That hint of smugness again; Sans decides he likes it, wants to see more of it. Wants to make him feel like he’s doing well, try and help him dissipate some of that shyness. Mettaton smiles when he nods, but then takes Sans’s hands and puts them on his hair and cheek respectively instead of going right back to it.

“I want you to show me how,” his tinny little voice says slow and sultry.

“that’s saucy as hell,” Sans growls appreciatively, letting his skull list to the side as he uses the tip of his thumb to open Mettaton’s mouth, then slides his pelvis forward a little more, tilts and presents. He smiles down at him, slides phalanges through his soft hair some more, then exhales tight as he coaxes him forward mouth first onto his quivering-wet pubis. He uses the tip of his thumb to push down on his lower teeth so they don’t hit anything hard, then thoughtfully slides the crux of his pubic bones between Mettaton’s soft lips. Oh. How about that. Turns out the inside’s _hot_ now, and that’s really doing it for him too.

“stars,” he whispers roughly. “gets nice n toasty in there after a lil bit, huh?” He groans deep again when a hum of agreement thrills right into him. Mettaton moans as Sans spends right into his mouth, and his hard, flexible fingers leave his lips to stroke his cheek encouragingly. “that’s real good for me,” Sans whispers, using both hands to coax him forward, seeing how much of himself he can get in there.

He’s wide and flat, but there’s a bit of a forward jut to his pubic crest. He moans as that soft, magic-damp tongue tentatively explores the smooth little bumps to either side of the joint. “you wanna use your tongue in the middle there?” he pants softly, and they both hear his deep groan again when he takes Sans’s suggestion. “that’s good,” he gasps, and it is. Soft little echoes of Mettaton’s desire and enjoyment pop like bubbles in Sans’s body as his magic dissolves into that silvery mouth.

Sans cups Mettaton’s cheeks, watches him carefully as he holds his head still and tries moving his pelvis just a tiny bit. He grunt and suppresses a shudder when he moans quietly, sending the buzzy-tonal vibrations into his bones.

“that okay?” he asks, and enjoys Mettaton’s enthusiastically affirmative hum almost as much as him pressing his tongue to the tight magic resonating in his pubic symphysis. He pulls back slightly, lets the shiver take him this time when his tongue follows until it’s out of his mouth.

He lets Sans hold him steady and slide his bones back and forth along Mettaton’s magic-slicked silicone appendage, making bold eye contact with a downright filthy look on his face.

“wow,” Sans whispers breathlessly, stroking under Mettaton’s eyes with his thumbs as his sockets widen. Gives him a wicked little idea. “almost looks like those human magazines when ya do that.”

The sound that comes out of Mettaton at that makes Sans spend out on his tongue and moan, and he hears a few metallic little clinks and clanks. Direct hit, apparently. That battleship's going down. Sans sees Mettaton’s shoulder start to move, his silvery eyes growing hooded and sleepy-looking. Seems like he doesn’t want to wait for Sans to do it, and that sure is giving him another tingly-sharp thrill now, isn’t it.

“you like it that much?” Sans gasps sincerely, then groans again when Mettaton nods superciliously with his tongue out, slicking up and down Sans’s tight little seam. He curses softly, watching the show Mettaton’s putting on between his legs while he holds his head again and just sort of...fucks his mouth, he guesses.

His breath shakes deep in and out and he feels Mettaton’s go ragged, blowing soft huffs into his pelvis through his nostrils. His exhalations are accompanied by pleased little noises as he touches himself with increasing vigor; the small part of Sans’s mind that isn’t utterly losing it with arousal observes that this is definitely the kinkiest thing he’s ever done.

“you working up to that little shiver?” Sans asks softly, stroking his cheek with his thumb encouragingly.

Mettaton growls affirmatively, then pushes his mouth forward until he looks less like a human magazine and starts to resemble a horse struggling with a bit. A crease appears between his soft black brows, mouth distorted wide around Sans’s broad pubic bones.

“holy shit,” Sans whispers shakily, then cries out as Mettaton somehow manages to seal his lips around Sans completely and _sucks on_ his pubis.

“o-oh, oh _fuck_ ,” Sans gasps with a high, surprised tone in his voice, then grunts and doubles over with the intensity of the sensation. Mettaton hollers into his bones deliciously, shakes and hums with his own pleasure. Then he darts his tongue light and repetitive into the tight magic coiled in Sans’s pubic symphysis… and does that sucking thing at the _same time_.

Sans tries to be gentle as he grabs his head to hold it steady, pushing himself helplessly into that ticklish-delicious friction and deep-drawing pressure; he barely recognizes his own shaky cry.

Explosive bursts of delight quiver apart behind closed sockets as he spends magic thickly in Mettaton’s mouth; the sensation is enhanced by the robot’s bone-gagged climactic shouts as he brings himself off on his knees with Sans fucking his face. His teeth close on bone _oh_ -so-gently; Sans lets out a strangled, desperate yelp as the hard surface sends the wobbly vibrations of Mettaton’s deeply satisfied groan in a wave right through every bone in his pelvis.

Sans eases out carefully even as delirious with pleasure as he is, protecting Mettaton’s teeth with his fingers again as soon as his mouth opens with a shuddering gasp. The robot falls away and pants hard, eyes screwed shut and moaning as his head lolls against Sans’s inner femur. Sans strokes his hair and whispers encouragement as Mettaton draws out his pleasure decadently, a few glitchtone hiccups happening as he shivers through the aftershocks.

When Mettaton finally opens his eyes and peers muzzily up at Sans, his mouth falls right into a sharp, gratified grin as his eyes narrow. Sans looks down and finally noticed his phalanges twisted into the front of his shirt, pushing cloth into the spaces between his ribs as he clutches his own sternum.

“heh,” he huffs with a weak, sheepish smile, “guess, uh. you got me a lil worked up,” he chokes out, pulling his hand down with a shrug. “sorry.”

“ _Did_ I?” Mettaton says with mock-innocence widened eyes, kneeling up from his sprawl to take Sans into his slinky-steel arms. He feels warm all over now; Sans can’t stop his soft, breathy moan or the deep shiver that chases it out. “I can’t imagine how...” he murmurs into vertebrae; Sans moans as that clever tongue pushes at them with an evocative little flicker. Hoo boy. “After all, I was just... _thinking_.”

He lies down on the couch and draws Sans down above him instead of looming; Sans really appreciates that. Then his dazed mind finally catches up with what he’d said: thinking, huh? Thinking about-

Mettaton gives him that same promise-edged grin, then draws him down close and caresses the front of Sans’s ribcage in the place he’d been clutching himself.

“You asked me if I-”

He goes suddenly silent, stares in the middle distance with a _very_ strange expression.

“You have _got_ to be fucking kidding me,” Mettaton says flatly.

Then he, um.

Faints.

Sans smiles tenderly, then uses his fingers to shut the silvery eyes.

“hey, don’t you worry. ‘m gonna get you back there lickity split.” Sans glances down, puts everything mostly back where it goes, neatens it up. Makes sure all the right panels are shut and latched.

He doesn’t turn around or anything.

“jus’ wanted to let you know, uh. ‘m gonna put my shorts back on fore we go.”

He waits a moment.

“i know where you’re at, so i won’t look if you don’t want me to, k?”

Sans wiggles and lurches off Mettaton’s body, grabs his shorts off the floor and puts them on. Slides his feet back into his slippers, then sits to the side and looks down at him for a lingering moment.

He touches the android form, then puts this other hand back over his shoulder and wiggles his fingers.

“if you wanna come with, jus’ go head and touch my hand.”

He waits.

A bitter, wispy answer comes after an unsurprisingly extensive interval of silence.

“…I can’t _touch_ anything…”

“it’ll still work,” Sans continues, calm and patient. “up to you, though. ‘m sure you can get there almost fast as me anyhow.”

He doesn’t feel anything, but he knows they’re all set anyways. At the next moment Mettaton’s body’s lying on the couch in Alphys’s lab, although the Royal Scientist herself isn’t currently in evidence.

“mind if i take a look?” he asks idly. “jus’ wanna check the battery. pretty sure that’s it.”

Another long interval of silence.

“...go ahead.”

Sans does, and it is.

“i’ll see if i can come up with something a little better-y in my spare time,” he quips; a thin snort rewards his effort. He puts the battery back, closes the panel and gives it an affectionate little tap.

He still doesn't turn around, just smiles down at the peaceful-looking, still form on the couch.

“kinda like sleeping beauty, huh?” he rambles, then shakes his head at himself. “you want me to do anything else before I go get alphys?”

“...I...no, no. It’s...fine.”

“you sure?”

He waits as long as it takes. He doesn’t mind; never has.

“Could I...have a hug?”

Sans knows what he means.

“sure,” he says quietly, then leans down and hugs the silent robot on the couch, gives a little squeeze and a grunt. Sighs and leans back up, smooths the soft black hair down.

“alright. m’ gonna go get alphie. you jus’ sit tight.”

“Th….thank you.”

“hey. it’s mutual,” he says, winks at nothing in particular.

Reality unravels as Sans takes a shortcut to Alphys.

A ghost floats over from the corner and gazes down at himself ruefully.


	3. Door Number Three

**Summary for the Chapter:**

> So! This took longer to write than I expected but I think it was worth it. More nuance. I originally intended it to be three chapters, but the last one was already longer than both previous ones combined so uuhHhh we’re doing four or five.

[door #3]

 

“…nice digs.”

Mettaton looks away from the big hole in the hotel lobby where his new fountain is being installed, glancing over at the saucy skeleton beside him. They’re the same height when he’s in his box form, and its lack of facial features helps him disguise his amusement. Instead, he lights up a big, red “thumbs down” on his display, adds a rude buzzer for maximum effect.

He suppresses a thrilled chirp of anticipation when he’s rewarded with Sans’s lovely, golden laugh.

“It’ll be much nicer once it’s finished,” Mettaton demurs lightly. “Much like the rooms were.”

Sans looks at Mettaton sidelong. The assessment through half-closed sockets is not nearly the idle glance it might seem.

Sans had performed his first show for Mettaton’s new hotel earlier in the evening. Although the audience had been limited to those working on the building itself and those who’d expressed interest in working inside it once the renovations are complete, the result had been a quite sizable crowd.

Despite the show being offered for free, many in attendance had tipped Sans heavily anyways. If Sans hadn’t already put his money away in his phone, he’d be jangling like sleigh-bells with every step. Mettaton can’t complain either. The largesse and hopeful atmosphere had put both of them in an unusually good mood, and Sans had practically leapt at the opportunity to go off with Mettaton and do something about it.

Well. In a Sans sort of way. Mettaton glances over as Sans chokes back what he’s 50% sure was a snore, then blinks like a cat as he seems to remember they were in the middle of something. Sans has a way of skewing the metrics when it comes to enthusiasm.

“y’don’t say.” The left socket slides shut again as Sans’s grin softens into a smile of heightened interest. The point in his open socket cards up and down Mettaton’s rectangular physique shamelessly. “that included in the staff tour?”

“You’re not _staff_ , darling.” Mettaton rolls slightly past Sans, then does the little dip that passes for a box looking over his shoulder flirtatiously. “You’re entertainment.”

Sans makes a pleased little hum, then starts shuffling after him at an unhurried pace that also somehow manages to seem springy. “…heh. that’s a way to put it.”

“If you insist,” Mettaton rebuts dryly, pushing the button to the elevator, “I can put several things a great many ways.” Sans doesn’t have a comeback for that one. But as those slippers drag-flop him past Mettaton and into the elevator, the way he lets the white points in his sockets stay locked on Mettaton until the last possible second when he’d have to turn his head makes him feel a bit like his square undercarriage just turned to pudding.

When they get to the room, Sans takes a look around at the gratuitously massive bed, the garish red lamps, and the astoundingly baroque portraits of Mettaton from several angles lining the walls. His grin sharpens as he renders his judgement.

“nice.”

“Of course it is,” Mettaton agrees, “this is _my_ room. Now, if you wouldn’t mind.” He wheels himself around demandingly. Then turns back when nothing happens.

Sans’s face has softened enigmatically.

“ya know you don’t gotta, right? i like how you are right now, too.”

His words coil to nestle warmly in Mettaton’s soul, almost as sweet as Sans’s magic.

“I may be a _Killer Robot From Mars_ , but I like to think I have a more stylish modus operandi than ‘keels over and crushes potential lovers by accident during foreplay’,” Mettaton demurs lightly as he approaches, despite being unexpectedly touched. But he has some things he wants to try out, and he prefers to have a mouth for some of them. The most recent battery design Sans had put forward had passed Alphys’s rigorous muster. Mettaton hasn’t fainted for a long time now.

“Flip my _switch_ , darling.”

And he waggles his square ass in Sans’s face like the true professional he is.

Welp, Sans is hardly the skeleton to resist a blatant temptation like that. When the glitter-splosion clears, he can see that this version of Mettaton’s android form is on the slinky side. Not quite as tall, and a bit more slight.

“heh.” Sans shuffles back rather than craning his neck to look up at Mettaton. He slithers out of his hoodie to make sure it’s obvious he’s not going anywhere, just giving himself a little room to disrobe with dignity. Not that he has much of that. “you on a diet or something?”

Mettaton rolls his silvery eyes. “Did you miss the part about crushing you?”

“awww, metta.” Sans flickers his eye lights in lieu of having eyelashes to flutter. “i didn’t know you had a _crush_ on me…”

Mettaton smiles as everything else drops away, and he lets it all show in his face. How much he likes this, how much he likes _Sans_ , and a hint of what he hopes will happen.

“Well, it turns out I do,” he answers breathily. Sans’s magic seethes across his skull so hard he pulls his shirt off in a hurry to cover it. He gets barebones quickly after that, still iridescent in the face but still having regained some of his composure. He should know by now this robot doesn’t have to be faceless to surprise him. And they don’t have to be in bed for Sans to get all flustered about it either.

But it helps.

Sans steps out of his slippers, picks them up and crosses to the other side of the bed to remove his socks, tucking them into the toes of the slippers and setting them on top of his lopsided pile of discarded clothing. He’s still trying to think of something unbearably sincere to say as revenge when Mettaton steals his thunder, such as it is.

“Enough _procrastination_ , sugar. Get on the bed.”

“…bossy.” Sans grins, his sockets ovalling happily. “…heh. ‘m into it.”

Mettaton gets a nice glimpse of the inside of Sans’s pelvis as he mounts the mattress, the innocent little curve of his tailbone a flash of faintly iridescent, living-bone white against impossible shadow of his integral magic as he crawls his lazy way up to the pillow. He flops over heavily down on his back with his legs tented up and his arms bent, thin phalanges curled at rest on his ribcage. Sans rolls his skull on the pillow until he can meet his gaze rather than bothering to lift it, arches a challenging orbital at Mettaton.

“see something you like?”

“A veritable _bone-_ nanza of coming attractions,” Mettaton sighs fervently. His soul flutters as one of Sans’s bent legs flops casually out to the side with the force of his delighted laughter. It’s gratifying to the slightly nervous robot, since he’d been saving up that line for the perfect moment and is glad to see it land.

Mettaton and Sans have been fooling around intermittently for a while now. Although Mettaton is hardly without throngs of admirers and interested parties, he’s rather partial to Sans. Maybe it has to do with the way he’d taken every single odd thing Mettaton’s evolving body has had to offer in stride (including them both being unexpectedly coated in springloaded leftover pudding that first time). Perhaps he can just tell that Sans loves the way Mettaton touches him, and likes to reciprocate just as much…if with more focus on conservation of energy on the skeleton’s part. Bit of a pillow princess, really, but Mettaton’s not complaining. He’s never left Sans’s company short (ha) of profoundly satisfied.

Or maybe this soft, warm glow in his soul’s because Sans had been noticeably overjoyed to fuck a topheavy, clueless, and surprisingly messy box a few millennia _before_ fucking boxes became fashionable. In fact, Mettaton suspects that Sans would be up for this no matter _what_ Mettaton looked like. Suspects he might even want to if he, if Mettaton was still… well. Nevermind _that_.

Sans looks to the untrained eye like he’s about to fall asleep, but Mettaton sees the bright opacity of the points in those new-moon slitted sockets and knows better. The robot clears his throat and pulls his fingers away from his belly, where they had been making a clutching motion identical to the one he’d provoked from the skeleton in his bed many times by now. There’s an excited little flare in those avid white eyes now; Sans doesn’t really miss a trick. He can tell Mettaton’s motor’s already running hot, and concluded he must have something fun planned.

Well, good. Mettaton’s not trying to be subtle. He’s finding himself more interested than ever in discovering why Sans came onto him in the first place…why he always seems so available to pass a little time in Mettaton’s arms. Never turned him down once, despite the fact that Mettaton’s had to pass now and then when Sans suggested going somewhere private. When his body’s been going through renovations less convenient than those currently happening at this hotel, when he was busy with another of his projects, or when he just wasn’t up for experiencing the exquisite vulnerability Sans always makes him feel.

Sans always takes it in stride, just like everything else.

Mettaton thinks he’s lost in thought, but he’s actually lost in lambent white points luring him closer without realizing it, until he sees them expanding to change focus because he’s only a few inches from them now. Mettaton comes back to himself himself on all fours, hovering over Sans who seems equal parts amused and aroused by his catch. Despite their banter, Mettaton hasn’t fallen on Sans once. Hasn’t ever come close to harming him in any way, and the size difference bothers the diminutive skeleton less than it used to. Mettaton earned his looming privileges through care, tact, and a remarkable talent for sucking on Sans’s pubic bones.

A skeletal hand reaches up slow, phalanges spreading as if to cup Mettaton’s face. Mettaton interrupts it with a playful grab short of its goal. He presses his artificial lips to the inside of the carpals to make Sans giggle with anticipation, then go quiet when he sees the heated promise in Mettaton’s eyes.

Mettaton does that thing where he takes his sweet-ass time running soft-silicone-over-steel fingers along silky-surfaced bone, teases each sensitive joint, caresses every juncture where the resistance that holds Sans together will heat up under his ministrations.

Mettaton’s also figured out with time and practice how to pleasure Sans’s permeable magic: the bigger fields in the space between Sans’s ribcage and pelvis, as well as the slightly more sensitive ones inside both. A lot of it has to do with focusing his intent, concentrating on how he wants to make Sans feel. Sans’s body-between-his-body reminds him of Sans himself. Omnipresent, thick with secrets, always hovering at the edge of untouchable.

In Mettaton’s not-so-humble opinion, that just makes it infinitely more satisfying to take him apart into a panting, magic-streaked mess.

He can see he’s doing well when San’s sockets get long and oval, then drift closed. Those nimble phalanges try to sneak in a vengeful fondle here and there at first, then just creep slowly up to take hold of the pillow to either side of his skull. Mettaton alternates circling his hand inside the ivory cage of Sans’s body, then spreads his fingers wide to let its slow oscillation resonate around and through his fingers. Sans shivers and grunts, skeletal hands tightening rhythmically.

“Do you like that?” Mettaton purrs from his position sidesaddle between bone legs, leaning his weight on the heel of his other hand, the shoulder pushed up fetchingly to lean his cheek against. Sans’s sockets stay shut, but a tiny crease appears between them as he nods fervently. He starts shivering with those delicate little clacks as Mettaton brushes his floating ribs lightly now and then, tickles across an iliac crest, lets his knuckles glance provocatively against his spine. Mettaton keeps teasing until Sans is panting heavily, arching up for more each time Mettaton’s fingers dance away.

Instead of giving it to him, Mettaton replaces his hands with his mouth and starts over from the beginning.

Sans stays quiet, because if he whines or bitches too much Mettaton will just stop entirely, and let him cool down before winding him up again twice as slow. Not that Sans takes issue with that. The whole reason Mettaton does this is because Sans loses his goddamn mind for teasing. He _loves_ it.

His magic is already misted up along his bones, his enjoyment offering itself to be sampled and savored. After Mettaton’s tongue passes, it beads up even more thickly. Mettaton can taste himself when he revisits, their pleasure mingling deliciously on Sans’s hard, smooth body. He laps it from the broad surface of his sternum, dips his tongue boldly into the intercostal spaces until Sans chokes on a moan.

“…fuck,” he sighs fervently. When Mettaton draws back, a light, almost musical clacking runs through Sans’s spine from skull to tailbone. There’s something precious and rare about that sound; it reminds him of Snowdin, one of the few places underground where the sheer size and height of the caverns allow something called wind. That’s a little how it sounds when its invisible force moves through the branches of the trees there, hardness brushing against itself in an audible caress.

Sans opens his sockets, the points inside broad and fuzzy with pleasure. He tilts his skull suggestively at the space in the bed beside him.

“gonna let me give you a turn now, foxybox?” He lets go of the pillow to wiggle his slender bone fingers, then brings them up to caress Mettaton’s face, run them through his hair.

“No,” Mettaton answers promptly, although he allows the petting, and leans in even closer as it continues. He’s rewarded with sincere surprise glancing across cool-white features, that surge of cyan-yellow iridescence teased to the surface by emotion.

They’re both a little surprised by Sans’s soft moan as Mettaton’s hand comes to rest on his bare sternum.

“You first,” Mettaton says breathlessly. It’s a question despite the structure, and it hangs gently in the humidity they’ve created in air between them.

Skeletal fingers slide up and over his own. An ambiguous expression shapes his malleable sockets, softens the fixed grin in a way Mettaton’s never seen before. Something hot and cold at once quivers through Mettaton’s soul; this isn’t something Sans is showing him...it’s what Sans feels, welling up unfiltered to be expressed on living bone.

“you sure?” Sans whispers hesitantly. A thumb distal toys with the tender wrinkles of Mettaton’s carefully crafted knuckles. Mettaton doesn’t answer, just lets Sans study his expression and arrive at his own conclusions.

“you wanna see me?” he whispers, breathily insistent. Never mind that Sans has let Mettaton know he’d be interested in this in a hundred different, subtle little ways that can be easily glossed over without anyone losing face. But he’s Sans. Of course he’d ask. Of course he’d make sure, even though there’s only one answer Mettaton has for him. Maybe the only one there’s been for a while now.

“Yes. I do.”

There’s a shuddering exhale, and Sans’s sockets hood the white points inside expanding, changing texture with desperate want. Despite his intensity, he’s not in a rush. He never is.

“yeah,” he whispers eventually. “yeah, okay.” He pats the pillow next to him. “c’mere. want you to hold me while i do it.”

“Of course.”

Mettaton allows those slender bone arms pull him down and hold him close, relishing the plush feeling of the resistance that holds Sans together resonating against his own body. It’s what makes Sans plump, although that’s more apparent when he’s dressed. The space between Sans’s bones is sensitive, although only the tightest joints and smallest foramina prevent physical bodies from passing through entirely. Those also tend to be his sweet spots.

Right now those joints are loose with arousal, and his smooth, hard body entangles easily with Mettaton’s. He pulls the robot close, but it still doesn’t feel like enough, somehow. Sans hooks a leg around that plastic-cased waist, ends up with his hand wedged between their pressed-together chests. So close, but he wants to feel closer.

_So close._

Sans turns his focus inwards and calls his soul, feeling and thinking, asking himself a little question. Asks himself if he wants to come out and feel good, come out and be _seen_.

“’m real glad you asked me,” he whispers as his fingers flex between them subtly. He feels its first gentle surge under his touch, hears Mettaton’s breath catch. “mmh. you feel it?” Mettaton’s forehead dips slightly against his, a tiny nod. “yeah…that’s me.” He thinks he hears a squeak in response, but that’s it.

Sans’s soul exists distributed throughout his body. There’s no part of him that his soul doesn’t occupy, that his soul doesn’t exist between. “want you to know something,” he continues breathily, still calling his soul, letting them both feel it answering. “hmm…more like...i wanna say some things.” He’s not in a hurry, and taking his time makes it feel even better. “think you already know…i wanted this for a long time.”

Sans lets his fingers creep into that soft black hair, distal points running along his scalp to make him shudder, cupping the back of his head like something delicate and precious. He uses it to guide him, to hold him steady while Sans traces those soft silicone features with his nasal bone.

“now that i said that, want you to know something else, too.” He pulls back enough that Mettaton can see his face. “maybe you figured it out already, but…mine’s not the same’s everyone else.”

“I know,” Mettaton manages, his artificial throat tight with desire and something even deeper. He hides it by kissing shed magic from Sans’s zygoma, making him moan softly with the pleasure of it. Mettaton’s hands roam the sturdy-yet-delicate filigree of Sans’s body, reassuring and needy at the same time. Every monster’s body is different, often varying wildly. They defy categorization in many ways, and although they can be a delight for selves and others, monster sexuality revolves around their souls.

Every monster’s soul is exactly the same, because they all share the same soul.

They are each a piece of an infinitely divisible continuum that nonetheless remains whole, an endless font of love-hope-compassion from which life springs in order to express that love. The pleasure monsters find with themselves and in each other is grounded in sharing that sameness. When they join and separate, they reenact the initial division. When they use their magic with intent, they can create a new soul out of their own, housed in magic and physical substance donated from their bodies.

But what if yours _isn't_ the same?

The same substance, but maybe with something a little extra others don’t have?

What if it _looks_ different, the same substance but facing the wrong way?

Maybe it doesn’t matter...or maybe it just _shouldn’t_ matter.

“gotta say this too,” Sans goes on, that low voice tight with need. “you want me to stop, jus’ say so. you don’t have to explain anything. i know you’re…skittish maybe, and it’s _okay_.”

“ _Sans_ ,” Mettaton whispers a little desperately.

“can i show you my soul?” Sans asks, expression pained with naked want.

Mettaton feels a sob thicken in his throat. “Please,” he whispers around it. “… _Please_.”

Air rushes out of Sans’s skull hotly. He presses his bone face to Mettaton’s soft-over-steel one and makes a small, vulnerable sound. They both feel his soul thrumming as he tightens all over, locking their bodies together for a breathless moment.

Instead of drawing his fingers back, his spine arches like a drawn bowstring to create a little space between their bodies. Sans’s shaky hum instantly sears itself into Mettaton's memory as one of the most beautiful sounds he’s ever heard. Sans presses Mettaton's forehead with his, rolls their faces down to look at what’s between them now.

A delicately iridescent, inverted white heart…but not pure white. As they watch, two colors pearl faintly over the surface, cyan and yellow curling inward to be swallowed into his depths. Colors like Mettaton has heard human souls have, but two instead of one, and combined somehow with the love-hope-compassion of a monster’s soul.

Because Sans is a skeleton, the only one Mettaton has ever met.

Sans’s soul hasn’t actually gone anywhere; nothing has been taken out. It’s just in two places at the same time. His soul’s still exactly where it always is, and it is _also_ condensed by his intent into this shape: exposed to be viewed or caressed, to be shared with someone, or for private meditation and pleasure.

Those impossible colors swirl again, teasing without withholding, hiding without deceit. And _so strong_. Stronger than Mettaton ever imagined was possible for a soul to be, to _feel_. Sans has wanted to do this with him for so long, even knowing (as he does now, in a way that cannot be ignored) that Sans doesn’t want people to know the way his soul is.

Mettaton had though Sans’s interest had been casual at the beginning. He’d revised that impression slightly since, but… even then. The winks, the smiles, the easy shrug at rejection. Those short bone arms, always open. But not open indiscriminately, he realizes now.

Open for _him_.

Sans had said from the first he might be up for getting closer sometime. The implication being the time and place of Mettaton’s choosing. Sans expressing his interest in ways easy to turn aside, saving face but letting Mettaton know it hadn’t gone anywhere. Those clutching phalanges at his sternum always falling away with a sheepish grin, Mettaton’s evasiveness met with Sans’s pretty little shrug, his encouragement and acceptance, a joke to lighten the mood.

There’d been nothing casual about it.

Mettaton thinks he hears something, but what he sees is too exquisite, feels too good, takes too much of his attention. He can’t think, can’t speak, can’t look away. Everything Sans _is_ hovers between them, soaking in Mettaton’s awe with a desperate thirst he’d never known existed.

Sans is the most beautiful thing he’s ever seen.

And when he can think again, he realizes the sound he hears is Sans weeping. And that what he _sees_ is an urgent need, tempered by the knowledge that his strength is overwhelming Mettaton, and he is nothing if not patient.

Sans’s phalanges curve in sharply, then hesitate. He needs to touch himself. He won’t until he knows Mettaton is okay with that, but Mettaton can feel the arm hooked around the back of his neck to hold him close shaking with desperation.

“Go ahead,” Mettaton says quickly. He wants to see it, and he’s not disappointed. Sans’s thin fingers slide right into himself as he exhales in slow, shuddering satisfaction. Sans’s soul is touching itself through the thin screen of his body. He’s in two places at once and now joined with purpose to center and soothe himself, those clever phalanges the conductor of his intent. Oddly, Mettaton feels the intensity of Sans’s presence ease as well, leaving him filled with desire but much more clearheaded.

He make a tiny, side to side rubbing motion with fingers spread, and Mettaton can _see_ how it calms and soothes him. The little crease between his sockets slowly eases away. When Mettaton makes an involuntary little sound of pleasure, those sockets open. The points inside are wide with both desire and its fulfillment, and he looks much more relaxed.

“Mind if I, um. Join in?” He taps a panel Sans knows well enough to recognize it by the sound. He also recognizes “shave-and-a-haircut.” Sans grins with delight, trying to find his voice; it can be harder to talk when souls are out, since it’s a little like speaking in two languages at once.

“mmh...heh.”His voice is slow and thick with arousal when it emerges, but once he starts it gets a little easier.

“hot,” Sans comments, his grin softening even as his eyes contract with interest. “go for it.”

There’s not quite enough room for him to do it as tangled together as they are, and Mettaton ends up kneeling between Sans’s legs again.

Of course once he gets there, he loses his nerve.

Sans touches his arm before he can get distracted by it, rubs phalanges up and down Mettaton’s arm soothingly. Shows him there are even more ways to satisfy a partner than there are partners to share them with. Shows him the possibility of exquisite pleasure that can expand in the space between what you show them in your soul, what you say with words, how you touch them, and the way you move together.

“You want to touch some more?” Mettaton asks with only a brief hesitation.

“yeah,” Sans assures quietly. Then he tilts his pelvis up at him to present his pubic symphysis suggestively, hot and thrumming, wet from all the teasing as well as what’s following it. “wanna rub it here?”

Mettaton’s breath catches; Sans can see how much he wants exactly that in his expression, and he shows Mettaton his own interest to match in his soul. The skeleton’s expression is soft and patient, anticipation in the shape of his sockets. Two phalanges cradle the point of his soul and rock against it, then draw down and spread apart to reveal desire blooming to the surface for Mettaton to see. He pushes in with his thumb on the other side, gives himself pleasure for them to share. Mettaton sees how good his mouth had felt earlier, how sensitive and delicate the crux of Sans’s pubis is. Sans shivers hard; shows him it’s okay if he doesn’t want that, either.

“we got nothin but time,” he whispers, letting his sockets slide half-mast. Then he shuts them all the way, as if he can hide what he feels with his soul exposed. He can’t, though.

Nothing but time...

It’s too true, and the truth hurts as much as always. Oops.

“...heh.” His deep voice cracks softly; a slow drop of magic slides from the outside of his socket, disappears around the soft-white curve of his skull.

Sans is fourteen thousand, two hundred and twenty four years old.

Mettaton’s a little older than that…probably.

They both peddle lies for fun and profit. Some of those lies are jokes, expectations built up to be confirmed or subverted. Some are entertaining stories: movies, shows, books, plays. Some of those lies are merely the mundane ones they live, stepping into these roles each day like a worn out pair of pants.

It’s the only way to survive.

And the only way to survive the roles they play is to strip each other down to the raw cores of who they really are when they need to. To ask for what they need, to say what they mean, to be vulnerable, to witness and accept each other… for as long as they both can stand it.

Mettaton kneels between Sans’s spread femurs, leans in on one hands, ready to try it out, see if they like it. Watching Sans’s magic mist the bones anew in iridescent readiness reminds him of something…kind of important.

Hesitation flickers across Mettaton’s expression. He pulls away to sit back on his heels. Sans smiles and waits; Mettaton’s visible difficulty tearing those silvery eyes away from his soul is a gratification unto itself, after all.

“I, ah, forgot to mention that this design brought back one of the more…messy side effects of the original?”

Sans grins silently. He remembers.

“This is different than before. It’s my… it’s pushed magic.”

Sans and Mettaton have only ever shared shed magic, part of their bodies deciding to become not-part of them involuntarily when it becomes agitated by strong emotions or physical exertion. It’s a delight to taste it, bliss to be tasted. But monsters can also make their magic come out on purpose, changed and shaped by specific intent. It’s what they use for healing, combat, communication, and reproduction. Monsters’ bodies are ideas become physical reality, the same way movement is an idea turned into an action.

“I wouldn’t do anything with your soul,” Mettaton hastens to reassure him. They both already know Sans only likes his own magic in his soul. He’d made it clear early on that he doesn't share his pushed magic either, even though neither of them have exposed their soul to each other before now.

“And obviously nothing would--” Mettaton lets out a nervous giggle. Just because magic pushed out with sexual intent _can_ result in a new soul forming, that only happens if it’s pushed directly inside the merged souls of two or more monsters. Mettaton’s soul isn’t even _out_. This wouldn’t be risky, just...very, very decadent.

Sans shivers, and heated fascination blooms in his soul.

“heh heh…yeahhh, i didn’t think we were tryin’ ta knock each other up.” He smiles up at Mettaton’s tense-shy expression as one of his sockets slides shut, touches himself to bring his unflagging interest and reassurance to the surface for Mettaton to see. “s’like when Dogs get real excited?”

Some monsters’ genitalia pushes a small amount of magic when they get their little shiver, often directly into their partners’ bodies. It’s said to enhance the sensation of pushed magic in the soul considerably. Sans has felt it on the bones of his hands before. Sans doesn’t have genitalia to feel it with but he does have hands, so like most monsters who do, he uses those to touch souls and push magic. He’s definitely a fan of his own taste, but he doubts he’d be interested in tasting anyone else’s.

Mettaton nods hesitantly; he knows about that, but not through personal experience or anything. Alphys had told Mettaton it was partially modeled after that process, even if the aesthetics had been cribbed from human sources. He takes a deep breath; despite it, one of his internal cooling fans activates with a low, audible hum. It’s as much of a tell as blushing, but he soldiers on.

“I was wondering if it would...” Mettaton’s voice glitches evocatively. “Can I…

Sans’s grin curves lasciviously.

“you wanna come on me, don’tcha.”

Mettaton can’t blush, but he definitely feels hot under the nonexistent collar.

“I just meant since...if I keep rubbing my cock here, once I get close I might, um-”

“…hey.”

“I just meant it’s fine if you rather we did something else? If you don’t want to get any on you, I, um-”

Sans is silent, and Mettaton finally looks up at him. Silvery eyes gaze into Sans’s soul and take in the excited interest there, along with something more complicated.

“you can do it right on there, s’long’s you clean me up after.”

After a moment of quivery hesitation, Sans shows Mettaton exactly what he needs.

If Mettaton wants to see evidence of his pleasure splashed on bare bones, Sans is _all_ for it. As for cleaning him up…

Sans’s face says “because i’m lazy”; his soul says _I want to be cared for, I want to feel valued_. Mettaton has to bite back a moan; the pleasure of seeing the gap between what Sans shows the world and what he feels inside himself…my _goodness_. That’s what he’d been alluding to earlier: vulnerability and want, an incredibly erotic peek inside what Sans keeps hidden behind that lazy grin, all those indifferent shrugs.

“I’ll take care of it,” Mettaton assures him, mechanical voice throbbing with sincerity. Sans lets his sockets slide shut as Mettaton carefully strokes his skull. Mettaton focuses on how he feels, then looks deep into the lovely cyan-yellow swirled soul hovering delicately between them.

_I’ll take good care of you._

Sans exhales shakily; he relaxes gratefully into the reassuring caresses, the steady gaze on his soul. Mettaton keeps petting Sans’s parietal as he takes himself in hand, then touches the blunt tip of his dick to Sans’ pubis. Sans shivers when Mettaton starts to rub it back and forth lightly, and after a minute or so Mettaton sees something good blooming in his silvery-iridescent self.

It’s the pleasure of what he’s doing to Sans’s body taking up space, entwining the with pleasure Sans is giving himself with his fingers. Mettaton focuses in on it, and uses his genitalia to make that pleasure expand as he watches carefully.

“oh shit,” Sans whispers softly, then his magic wells right up under Mettaton’s cock, his natural sweetness sharpened with what they’re sharing. His next exhale’s a moan, and Mettaton sees a twinge of something he recognizes easily.

“You’re _beautiful_ like this, darling.” Mettaton hears his own tinny little voice reassuring him, tight with his own pleasure. Sans shivers and hums plaintively; he feels a little conflicted but Mettaton keeps moving against him, keeps petting and whispering encouragement until those bones loosen, until he starts to feel almost floppy. “You’re _always_ … you’re so lovely, you taste so sweet…”

He means every word, and his regard chases Sans’s insecurities around until they start to melt under the pleasure Mettaton’s body gives him, under his own touch soothing him expertly. Mettaton’s gaze is steady for several long, lovely minutes; he doesn’t look away until pleasure and care push everything else out. The crooked, narrow gap of Sans’s mouth falls open with bliss as he slowly forgets to feel self-conscious about how he looks, a thin wedge of darkness that narrows into nonexistence as it approaches the fused right side of his mandible.

It’s nothing Mettaton hasn’t seen before; Sans eats in front of him as much as you’d expect. But it’s more like… Sans doesn't think it’s something anyone would want to see during _sex_ , as if his face itself is an unflattering expression, the shape of his mouth an unseemly grunt. Mettaton keeps watching, keeps acknowledging those twinges of insecurity until they finally dissolve away into his acceptance. Still there, but no longer a barrier between them anymore.

Mettaton’s breathing goes ragged; he can see that Sans has just as much trouble with being vulnerable as Mettaton does.

Sans cries out when Mettaton switches to running his entire length along his slick little seam, using his thumb over the top to apply steady downward pressure. Mettaton nearly chokes on delight as the smooth twin bumps of Sans’s pubic tubercles stimulate the underside of his cock deliciously. The tense bud of shadowed resistance that holds the joint together thrums between them.

“Is it good?” Mettaton gasps softly. “Can I do it harder?”

Sans cracks his sockets open, the points inside wide and fuzzy. Sans is afraid to be handled carelessly, and he also very much trusts Mettaton with his delicate body. Sans reaches up and takes his soul in both hands, manipulating it lightly while he thinks about it.

“yeah,” he whispers, and a bead of magic wells up to slide down one of the deep grooves beneath his socket. He mewls softly, tenderness blooming in his soul as Mettaton brushes it with his finger, then lifts it to his lips with a sigh of bliss.

He palms Sans’s iliac crests to hold his pelvis steady, then moves his own hips to slide the length of his cock gently along the slickness at his pubic symphysis. He watches that lovely cyan-yellow soul carefully, makes sure Sans enjoys it. Turns out he loves the sloppy thrill of Mettaton gently taking his pleasure on sensitive bones while Sans does himself just how he likes it.

He sees a bloom of surprise-( _lust_ )-concern when he leans in a little too hard; Sans lets out a soft, sweet gasp when he eases up the pressure and moves faster instead.

Turns out that’s what gets him there. It’s nice when that sort of thing works out for everyone, although Mettaton...he needs just a little, a little _more_ and then it’s...

“It’s happening,” Mettaton gasps, lets Sans’s pelvis rest in his lap. He leans on the heel of one hand, pulls away just enough to circle his genitalia with the fingers of the other. He keeps the tip flush against Sans as he strokes himself quickly to the edge, silvery eyes watching carefully. He gasps, then a small, tight noise jerks out of his throat.

The overflow of magic isn’t forceful despite the white-hot pleasure of its emergence stealing his breath. Mettaton lets out a strangled moan as it wells modestly at the quivering opening, uses his thumb to push the blunt head of his cock firmly up and down the resonant seam of Sans’s pubis. His grip tightens as it travels towards the base of his length, and Sans can feel it shaking back and forth with Mettaton’s frenetic tugging. It’s a light, flickering stimulation that makes Sans’s voice break as Mettaton’s magic spills over to flood him with unexpected heat.

The circle of his fingers moves quick-short, every few strokes resulting in a fresh blurt of wet, astringent warmth. The clear magic slicks his movements, thickly coating quivering bone until it overflows to runnel into his sacrum.

The part of Sans’s mind that’s still processing stuff like ‘thoughts’ notes that he’s apparently more sensitive to this kind of magic between his legs than on his hands. Nice.

Sans’s breathing is ragged; he looks so beautiful sprawled out under Mettaton, legs open and pubis presented, that he feels compelled to reach down and cup his skull gently. His own magic sheds in delighted response to mingle with Mettaton’s. Sans turns his skull in towards the robot’s touch, sockets narrowing as Mettaton caresses the side of his skull. Mettaton strokes his zygomatic process with his thumb, encouraging the intent he sees in Sans’s soul.

Sans loves the syrupy sensation of Mettaton’s magic soaking him, laden with his partner’s pleasure. He looks down his body and sees the thick, clear iridescence trailing from his pubis down into his sacrum, puddling across the flat and into the foramina there, pooling against the integral magic tight-packed inside. His skull hits the pillow with a moan, bones going loose while Mettaton continues massaging his soaked pubic symphysis with the blunt head of his cock. He gives himself a few firm strokes from the base to press out the rest; it trails down gamely as Mettaton shivers through an aftershock.

Sans looks at Mettaton’s expression, downright drunk on what he’s feeling and he’s still rubbing Sans there, still making sure he’s giving him a good time. God, it’s too much. He’s ready.

The tips of Sans’s phalanges crook as he takes short, hitching breaths. Spindly fingers shake as they tighten briefly above Mettaton’s knee, then relax to pet soothingly.

Sans’s moan is dripping with profound satisfaction as he pushes his own magic into his soul.

The points in Sans’s sockets dilate until he closes them, until he turns his face into Mettaton's palm again, nuzzling and huffing hot, ragged breaths into it. Mettaton’s transfixed; he can _see_ Sans’s body penetrating his soul, watch right where his magic becomes not-part of him with his intent, sees how good it makes Sans feel. It’s like watching a thick paint pouring into a thinner paint of the same color, wavering into him like sugar dissolving in water. Like something both whole and infinitely divisible, two things becoming the same thing as he watches.

A hand leaves his soul to hold Mettaton's hand tighter against his face. Sans presses his teeth there hard and moans rhythmically into the soft palm, surrendering to his need and filling up his soul with as much of his body as it can hold. This isn’t only a touch. Sans’s body _becomes_ his soul when it goes inside. This is the connection between self and self with every barrier removed; Sans gives Mettaton the ultimate expression of his own wholeness.

Eventually he makes a quiet hiccuping sound, then a softly ragged, satisfied exhale. Sans stops pushing his magic and opens his sockets to look up at Mettaton with a naughty little smolder. He holds the robot’s gaze like a vice as he feels a bone hand slide frictionlessly across his back; the hand Sans is touching his soul with changes positions until the silvery-cyan-yellow light is slatted by metacarpals between them.

Then Sans lifts his chin and pushes his soul back into himself hard; his other arm pulls Mettaton right down on top of him with a low growl. He arches his spine as the growl gets louder, then expands to a deep-vibrating purr of delight, echoing the flood of his soul back into itself, carrying Mettaton’s gaze, his own magic, and what they’ve just shared along with it. Mettaton’s voice adds itself helplessly to his when he feels the echo of Sans’s seething-full soul crashing back into him, along with Sans’s profound satisfaction wavering up into him like steam from a Hotland vent.

Mettaton’s too tall for their hips to grind with their chests pressed together, Sans’s incongruously sinuous arms and legs wrapping him like a segmented bone octopus. He moves under the robot’s steel weight, undulating and grunting as they savor Sans’s repletion together. Mettaton barely notices he’s rutting damply against the bedclothes until finally Sans relaxes back into the soft mattress, lets him go with a throatless sigh and a lingering caress.

Mettaton leans up, gives Sans a wicked little smirk of his own.

He’s got a promise to keep, after all.

Mettaton reaches down his own body and gathers up a little of the slick along the top of his cock with a thumb: Sans’s light-sweet shed magic, and the complex richness of his own climax. Sans’s sockets widen, the points inside trapped by those silvery eyes as he laves his tongue down his damp digit from base to tip. He shudders when Mettaton winks.

“oh shit,” Sans observes mildly, then is quickly reduced to incredulous moaning as Mettaton decides to lick him clean. His phalanges creep down into Mettaton’s hair, tighten a little hard, the relax again quickly.

“i literally meant like. washcloth or something. suh...s-square of softpaper, maybe. don’t gotta-”

Mettaton’s wide, flat tongue gathers up warm slick on the inside of his femur, and Sans _squeaks_.

Sans pants and stares at the ceiling in wonder; he probably shouldn’t be surprised by now. But...he is, apparently. Surprised. Getting off hard too, (more than) a little flustered. Sans makes another faint, high noise, then looks down between his tented femurs.

Mettaton touches the flat of his sacrum again with a fingertip. Sans manages to bite back another squeak.

“Well?” the robot says teasingly.

Sans tries to stare down at him, panting heavily as the contents of his skull swirl so hard he looks like he’s having trouble remembering what words are.

“Flip _over_ , darling,” Mettaton purrs, and Sans nods fervently. After another second of witlessness, he actually manages to lurch up onto all fours.

Sans paws a wad of blankets up under his body to support his weight, then sticks his ass out with a dazed little huff of anticipation. That apparently doesn’t prepare him for the molten reality of Mettaton’s suddenly (shockingly) mobile tongue dipping into his sacral hiatus, searching for traces of his own magic inside. Surprised, breathy moans escape him as he does the same to each little hole along the wide, flat bone, patiently working his way down until he mouths the very tip of his coccyx. He flinches back, grabbing the wad of bedding hard. Mettaton pulls back as he whines either for mercy or in protest, palms the knobs of his femurs soothingly.

“ _fuck_ ,” Sans sobs breathlessly.

Mettaton’s not sure if that’s a good fuck or a bad fuck, so he asks.

“do you like that?”

“….fuck,” Sans repeats shakily, taking the opportunity to let a hard shudder take him without the worry of busting Mettaton's teeth with his tailbone. Or vice versa. “...yeah. go ‘head.”

The surprised little coo Sans lets out into the wad of bedding when Mettaton touches the tip of his tongue to Sans’s coccyx again makes it very difficult for Mettaton to resist the urge to rub his cock some more. But seeing as he is a true paragon of self-control, he merely frots distractedly against the bed so he can concentrate on what his mouth’s doing.

At some point it goes from cleaning up his own spend to both causing and cleaning up Sans’s. He keeps on going until Sans is a sobbing, limp mess, and Mettaton's holding him up with his hands while he finds out how much of Sans he can get in his mouth from _this_ direction. Turns out it’s a lot.

“f...f- _fuck_!” Sans makes a strangled, wordless sound instead of the “yeah”s he’s been peppering his fascinating vocalisms with, then adds, “s’enough…” Mettaton draws back carefully, but once he lets go Sans just...collapses. Looks like one of those blunt-tipped bone claws actually tore a _hole_ in a pillow.

Oops. On multiple levels.

Mettaton lies down gingerly next to Sans, who to his surprise turns into a bone octopus once more, wrapping his floppy-hard body around him like a vice.

“m’okay,” he mumbles weakly before Mettaton can ask.

“Are you sure?” he asks anyhow. Bone fingertips clack-rasp on his plastic-cased back, somewhere between twitching and soothing. Sans shivers, sucks in a deep breath.

“...yyyyeah _hhh.._ _hh..._ ” he exhales lasciviously. Something prompts a last tiny squeak from him; Mettaton doesn’t know what, but those bone limbs tighten even more, then shake and relax. “don’ lemme go,” Sans slurs, and then-

…okay.

That’s _definitely_ a snore.

At first Mettaton feels slightly miffed, but it shifts to mild embarrassment when he recalls that his lover is unusually delicate, and he obviously pushed him a bit too hard. He’d also been pretty adamant about not wanting Mettaton to go anywhere, and combined with what he saw in his soul….well. Mettaton doesn’t plan on it anytime soon. Certainly not before he wakes up.

The embarrassment deepens when Mettaton remembers it’s also traditional to feed one’s lover in bed, to replace any magic (ahem) _utilized_ during the festivities. And it’s not like he didn’t already know Sans needs a lot more sleep than most monsters…he might need more to eat afterward, too.

His smile softens, and he has a moment to appreciate Alphys’s insistence on adding a compartment for his phone in his arm. He pets Sans’s skull for a minute, which rather adorably makes his bone arms tighten, then gets it out.

_One of everything to Room 204 in_

…

Mettaton frowns, and sends a message to Alphys instead.

_How long does Sans usually sleep for?_

She answers very quickly, then Mettaton has to put her feed on hold when she immediately sends at least 13 nigh-simultaneous and increasingly invasive questions.

Mettaton brings the other interface back up, sends the room service order, then settles in for the long haul.

“I’m not going anywhere,” Mettaton whispers. Another promise he intends to keep, heard or not.

 


	4. The Fourth Wall

**Notes for the Chapter:**

> I wanted to put note here if you got this far, because perhaps it isn’t clear despite the tags.  
> I wrote whatever this is because trans people have sex with each other and I don't think there's enough stories about that.  
> Seems like when you even find trans characters at all, it's someone who's trans having sex with someone who isn't. The vehicle's a little different here, but I think that helps rather than hinders in conveying the kind of emotional truths and interactions involved. In this story the characters become closer and more intimate by having sex, and it’s okay to do it that way. The emotional stakes are high, but not for the reasons you might expect.  
> Sex doesn’t have to be the same story over and over, and I wanted to show how meaningful it can be without it having to mean any specific thing in particular. Their dynamic's purposely ambiguous but I wanted to show there can be a lot of powerful feelings and intense connections in the spaces between curtain calls.  
>  **I wanted to explore and show how amazing sex can be when you don't have a boatload of assumptions about what your partner's body is supposed to be like, or what ways they're supposed to enjoy sharing it.**  
>  So I wrote a story about a literal skeleton and a metal box/transitioning android having a bunch of really good sex because they came together without assumptions, and instead actually communicated and gave a crap! That’s something I think anyone can enjoy and celebrate.  
> Nevertheless. This is a story about trans people having sex with each other metaphorically, metaphysically, and literally. 
> 
> Joanna Newsom – Clam, Crab, Cockle, Cowrie  
> https://youtu.be/F-xUpdO3g44

“you fancy a bite of this feast you ordered?”

Sans brandishes a flat utensil, its tip daubed liberally with the contents of an open tin can with a picture of Mettaton in cat-ears on the label.

He’s lounging at his bare-boned ease in Mettaton’s hilariously massive hotel room bed, pleased as pie to be the center of attention for his audience of one. Waking up to a rickety-wheeled cart of everything on the menu had been a nice surprise, and Mettaton’s apparent determination to hand-feed him until he doubles in size like a big yeasty ball of dough is an unexpected bonus.

Sans hasn’t ever seen Mettaton eat or drink anything; although he presumably derives nutrition from something or somewhere, he hasn’t chosen to share that information with his skeleton lover as of yet. Sans keeps his question casual and specific, since all he intends is to find out if Mettaton would like to be fed in turn from the supplies at hand, but it looks like that’s a no.

Mettaton shakes his head, then tosses it so his hair flops over one eye like it’s designed to.

Sans knows a sore spot when he sees one, but he also knows just the thing to perk up a flaccid android.

Something to put the _bone-back_ in his _backbone_ , so to speak.

“welp,” he sighs, arranging his features into a mock-innocent expression, “spose i’ll jus’ have to feed you something else then.” Mettaton glances at Sans suspiciously; he really should have seen this coming.

Sans pulls the blanket down and fondles his own pubis, presses a light suggestion to Mettaton's shoulder with the other hand and a teasing browbone wiggle. Then he falters, because Mettaton not only declines his suggestion, and gives him a mildly exasperated look that takes him aback for a second. It’s Sans’s turn to wilt; it’s not often he misreads the room.

“It’s hardly _feeding_ me, darling,” and Mettaton actually rolls his eyes, “if you expect _me_ to do all the work.”

Mettaton lies right down on his back with his hands folded like a sleepy princess, closes his eyes, and opens his mouth.

And waits primly for what Sans can only assume is his—ahem—recommended daily allowance of supplemental calcium.

“holy shit,” Sans mumbles faintly, moderately impressed by Mettaton’s boldness. Then he makes the noise that accompanies straightening out wavering magic between where his voice comes from and where it comes out, which is more or less the same noise other monsters make to clear their throats. So maybe he’s a _lot_ impressed. And now it’s been like a minute straight of that silvery tongue waiting patiently.

Wow. Mettaton’s seriously just gonna call his bluff like that?  
“uh...you got it, metta,” Sans says limply, flops around and crawls over, throws a bone leg over the sauciest robot _ever_ , and carefully straddles Mettaton’s face. Mettaton moans dramatically as Sans’s ischium touches his tongue; a sharp breath huffs out between Sans’s teeth when he feels it. He grabs the headboard for balance, then shifts so that magic-damped appendage traces the inner curve of one ischiopubic ramus, then around the other side. He has to choke back a whimper when that wicked little tongue darts over to lick at the tip of his coccyx again.

Sans leans forward and tilts his pelvis up slowly, curling up like a snail as Mettaton turns his head to pepper kisses around the entire rim of Sans’s pelvic outlet. Sans’s body keeps on curving, like it’s being drawn in around the barrage of pleasure at his core, and it doesn’t stop until his frontal bone meets the headboard with a light thunk. Mettaton opens his eyes, all wicked mock-innocence even with his mouth full.

Sans manages an appreciative, surprised little laugh.

“still feelin’ peckish?” Sans has to suppress a shiver when Mettaton’s affirmative hum buzzes against his unyielding hardness. Sans grips the headboard at the top to free a hand, leans his forehead on his radius to peek down at the action in comfort and style. He pulls his pelvis back just enough to touch Mettaton’s lips with his thumb.

“okiedokie…open wide for the trombone lesson…” Mettaton giggles at Sans’s playful singsong; he’d already parted his lips again as soon as Sans touched them, but Sans wants to make sure they don’t have any uncomfortable points of contact considering the new position. He uses his thumb between his lower teeth and his pubic bones as a guide, slips himself right in there and gets comfy. Mettaton’s hand comes to slide warm fingers around Sans’s femur, gives him a little squeeze of encouragement.

“good thinkin’,” Sans sighs passionately as he nudges the sensitive crux of his pubic bones around in Mettaton’s hot, clever mouth. “jus’ gimme a little tap if you need me to ease up. twice to stop.”

Sans had intended to take advantage of the captive audience, but the only sound he ends up hearing are his own shaky breaths quickening in and out of his skull, his frontal bone rasping along his arm until it clicks to rest the crook of his elbow. This always feel good, but there’s an extra layer of _something_ about doing it this way.

“metta...” he whispers, moaning at the answering hum traveling through his pelvic bones, the gentle squeezing of those clever hands around both his femurs now. He’d usually have taken his thumb out by now, but for some reason it just keeps sliding back and forth in there between his pubis and Mettaton’s lower lip over and over as he tickles his other fingertips along Mettaton’s jaw gently. When Mettaton moans again, Sans’s magic spends sudden and sweet in his mouth; they moan again together at the strength and complexity of what he’s feeling. There’s a tap on his femur; Sans pulls back immediately.

Instead of saying anything, Mettaton takes Sans’s thumb and forefinger in his mouth and starts sucking on those, swirling his tongue around and poking at the joints through the suction.

“oh fuck…” Sans gasps weakly, letting go of the headboard so he can shimmy down close, lying right on top of Mettaton’s lithe, slowly heating body. His other hand cards itself absently through soft black hair, but Sans can’t take his eyes off Mettaton’s glossy lips pulling his bones deeper inside. Sans pulls them out, then positions the tips of his first two fingers curiously at Mettaton’s lips instead, folding the thumb back underneath.

“yeah?” he whispers raggedly, then moans in astonishment as Mettaton sucks them in, eyes smoldering with a promise his mouth fulfills at once. Sans is utterly delighted when Mettaton offers his hard-soft thigh to rub between Sans’s femurs, and he grunts softly at the combined sensations.

When Mettaton’s hand comes to rest on his ilium, guiding him up and down just the way he likes it, Sans turns Mettaton’s head slightly so he can lean on that elbow. It frees his other hand so it can roam his lithe-slinky, silicone and steel body, but he only watches what Mettaton’s doing with his mouth. He adds another finger, and everything gets even better.

“jus’…i-i wish...” Sans bites off a strange little sob, wistfully pressing his teeth to his own wrist as he fingerbangs Mettaton’s mouth fitfully. He doesn’t know how to say this, or what he wishes. He’s just so _full_ of whatever this feeling is, he might actually explode with it.

Or, you know. Might spend about a gallon of that feeling all over the ridiculously sexy robot leg he’s humping like it’s the last thigh on earth. Since that’s what happens.

Sans delicately touches a question to the panel that houses Mettaton’s genitalia with his free hand. It’s hot to the touch, a good sign. Sure enough, Mettaton moans ragged encouragement around his fingers, and the panel slides away to let Sans’s nimble phalanges find his cock inside. He coaxes it with a practiced motion, uncurling it from its protective housing, and gives it a slow, gentle pull to help it click into place.

Sans touches lightly along the warm shaft, then slides the loose circle of his fingers along its length. His thumb teases the soft little opening at the tip where his magic pushed out before, and Mettaton makes a low, staticky hum of pleasure, eyelashes fluttering becomingly. He purses his lips around Sans for a moment, then pulls back so he can suck Sans’s pinky in his mouth too along with the rest. Sans curses softly, then louder when Mettaton takes him in nearly all the way to the carpals.

He adds that enthusiasm to his already-fervent handjob, and they both just kind of lose it for a while. Sans can’t stop shaking; this makes him feel almost like… as if his hands give Mettaton so much pleasure, he’s trying to give them… pleasure back? Sans doesn’t know, doesn’t have a goddamn clue and he’s not even sure what this is but holy shit is it _ever_ doing something for him, and he gives himself up to it completely.

He’s not even sure how long it goes on for, but at some point they both kinda realize Sans is lowkey crying, and maybe they should check in a little. Sans squeezes his trembling femurs around Mettaton’s thigh; a short sob escapes him, and more magic beads up at the inner corners of his sockets, slides down the deep grooves beneath them.

Mettaton takes Sans’s phalanges out of his mouth slowly and gives them a sloppy kiss before letting go; Sans moans in soft surprise when those mad, roaming kisses find the spent magic misting his mandible, his maxilla, even right on his teeth. Then that mobile tongue darts right into the corner of his socket, delicately depositing a taste of Mettaton’s faint astringency, mercilessly laced with Sans’s own insistent sweetness, the sharp pleasure of his emotions.

“... _fuuuck_ ,” Sans hears himself whine shakily about a million miles away; his neck cranes back involuntarily as he shudders from skull to toe. A little embarrassing, but this feels too good for anything else to get a foothold. Mettaton’s desire is absolutely _saturated_ into that spreading watercolor emotion; Sans is so wanted, so _beautiful_.

And a hint of something even deeper twines through it all, something they’ve both been flirting with for a long time now. Mettaton teases the hand away from his cock gently, pulls Sans tight against him to lick at his cervical vertebrae while he places those delicate bone fingers on the circular panel right over his belly. Then he squeezes, bathing Sans’s neck in a shuddering, staticky exhale.

Sans barely recognizes the raw sound that emerges from his own skull.

The belly’s where most furry monsters expose their souls from… And this panel’s certainly the spot Mettaton clutches himself when things between he and Sans start to feel saturated with a _particular_ brand of hot-and-heaviness.

He always takes his hand off when he notices and glances away shyly.

He’s certainly never clutched Sans’s fingers tight to it that same way, never pulled him close like he’s ready to eat him up with kisses, never started whispering little pleas, broken glitchtone moans and pieces of words that mean...like he’s, like Mettaton wants _Sans_ to…

Sans pulls his face back a little and tries to get a breath in, but he can’t hold back a shaky moan when he sees Mettaton’s half-dazed, half-frantic expression. He doesn’t try to get the hand Mettaton has pressed to his belly back, but he frees the other so he can touch Mettaton’s face, stroke his cheek while they both calm down a little. Mettaton’s perfect black brows are creased; he’s panting and chewing his lips. Sans just waits, petting and shivering intermittently until that crease smooths out a little bit.

“metta...”

The hand tightens over his; the pained expression returns.

Sans keeps his focus steady on Mettaton's silvery eyes as he shakes his skull oh-so-slightly, then gently replaces his bony hand with Mettaton’s own and pats the back of it soothingly. They’ve been doing stuff for a long time now, but this is the first time they’ve gotten their souls involved so directly.

Sans could probably coax Mettaton’s soul out with Sans’s slow, patient call, but something deep inside Sans wants this to be Mettaton’s doing. He wants _Mettaton_ to show his soul Sans, choosing to reveal himself in his own time, under his own steam. There’s something that feels balanced and right about doing it that way, the same way Sans had brought himself out to show Mettaton.

“you wanna show me?” Sans asks; his soul twinges deep with want when Mettaton nods. Mettaton looks confused at first when Sans pulls away and starts to crawl up, but Sans smiles and points at the headboard with his chin. “c’mere. let’s get comfortable.”

He directs Mettaton to sit with his back against the headboard, then Sans clambers heavily into his lap, straddling him. His cock’s still out, and Sans shimmies up until the base is wedged under his pubis. He shifts forward until its length is pressed against Mettaton's body, so it doesn’t move around or get in the way. Sans tilts his head, narrows his sockets at it for an extra second or two as he puts his hands on Mettaton’s shoulders, then huffs in amusement.

“…heh. kinda looks like i got an upside-down dick right now,” he rumbles softly, and Mettaton snorts and snickers. The tension eases out of his shoulders under Sans’s relaxed hands and soft, just-for-them-in-private grin, and they look back into each others’s eyes for a long pleasant moment.

Sans smiles and tilts his skull, looking at Mettaton’s face like an especially pretty pinecone, rubbing under his ears with his thumbs and fingers interlaced behind the solid steel column of his neck. He shivers when Mettaton’s hand finds his shoulderblade, sockets narrowing happily as he rubs a little circle there. His other hand’s on his belly, and his expression grows thoughtful, introspective.

“mm...” Sans sighs, “yeah. feels good. s’okay if it doesn’t wanna come out yet, either.” He hums a little, tilts his face down to watch Mettaton calling himself. Sans had been right, he does it right over his belly. “no harm in asking.”

Mettaton’s breathing deepens; to Sans’s surprise, the hand on his shoulderblades teases up to his vertebral processed, threads between them to pull Sans closer. He presses their faces together until Sans can’t see what he’s doing anymore, makes up for it with hot little robot kisses all along his chin.

“I’m…different too. Y-you’ll be able to see it.”

“i figured,” Sans whispers, magic seething across his skull with excitement. Mettaton’s hot breath tickles under his mandible deliciously. “doesn’t change anything.”

Mettaton’s breath catches. “I want you to see,” he says, tinny tenor shaky with emotion. “I _want_ you to-” He gasps, pulls Sans back so he can watch.

Mettaton lets out a raw glitchtone sound as his soul emerges, the same silver-white as a monster’s soul. Because it _is_ a monster’s soul, despite the point facing down and twin curves arching above.

His soul’s upside-down… just like Sans has heard human souls are.

Because apparently Mettaton is a ghost.

Ghosts, of course, being monsters who didn’t become monsters in the usual way. Rather, some aspect of them was once human, and through unknown intent or accident of fate their souls joined the monster continuum rather than going wherever human souls go when they die. Sans doesn’t really know where ghosts come from, but he doesn’t know where _he_ came from either. It’s not really a big deal, nor is being a ghost.

The only note of import is that Mettaton obviously doesn’t want anyone to _know_ that, and only insofar as Sans sure as hell isn’t going to tell anyone. It suits Sans just fine that the funniest pun underground is between his legs right now, a literal _ghost in the machine_ , all the better for being something private.

Something just for _them_.

Sans supposes that might be why Mettaton had been so shy about getting souls involved, but who knows. It certainly doesn’t bother Sans, and Mettaton’s breath hitches faintly when he feels the desire in Sans’s gaze.

Mettaton’s tiny-surprised flutter of pleasure floats right up like a sweet little echo flower.

Sans’s whole face goes soft with wonder. So many layers, so much to see. So _beautiful_.

Mettaton moans in breathless surprise as Sans’s eyes focus and delve, that incisive gaze tickling into him with care and compassion. Like he’s...he’s teasing, but also _giving_ him what’s being teased. Sans’s gaze in his soul feels like a promise kept; desire and its fulfillment at once.

“’m only gonna look at what you show me,” Sans whispers tenderly. “an ‘m gonna be _real_ easy when i do it, okay? i can tell you’re...” he trails off.

Sans lets out a long, awed breath; he shivers and rubs soothing little circles on the sides of Mettaton’s neck with his thumbs.

“you never did this before,” he whispers softly. “…thanks.”

He lets his phalanges creep up into Mettaton's silky black hair as he watches confusion muddle across the surface of the lovely soul that’s utterly transfixed him. Sans laves his focus over it gently, teases it out until Mettaton makes a soft little click in his throat.

Mettaton doesn’t know what he’s being thanked for.

“for trustin me with it. ‘m glad you did.”

The confusion clears, quivers into something heated and needy that fights against something else Sans doesn’t look at too closely. One thing at a time.

“you should touch if you want to.”

Mettaton’s fingers slide in, calming him only a little. Mettaton’s breath sobs in and out, his mechanical voice decorating each soft little huff. He shivers, then just hums and closes his eyes

“s’okay if it’s a lil hard to talk,” Sans assures him. “was hard for me first time i showed someone, too.” He smiles softly at the memory, the desperate noises and throaty sobs he couldn’t keep inside. Mettaton’s a regular cucumber in comparison.

“mmhmm. cried like a babybones.” Sans makes a soft little huff, thinking about earlier. “...guess i still do….heh. never knew anything could feel that _good_ ,” he rambles, letting his eyes roam, concentrating on the insecurities he sees chasing themselves around, trying to hide underneath each other.

Mettaton’s never showed his soul to anyone because he didn’t want them to know what he _was_. Didn’t want them to see that he’s not entirely sure if he still is, was, or will be; but mostly he didn’t want them to see the unsureness itself. He only wants people to see what he shows them. Wants to control the way he’s perceived. Sans sees that, he _acknowledges_ it.

Mettaton’s spine arches; he gasps and shudders up tight for a second, then relaxes.

Sans’s gaze caresses his fear of rejection the way bone fingers caress his body; he beeps helplessly as the slow honey of Sans’s regard pours into the desperate need he hadn’t known existed before it was filled. Sans _sees_ him. Those lambent white points are roaming inside him, swirling delicately around everything he is, was, and could potentially be.

“sh-sh-shh, yeah, i know. i see it.” Sans takes a slow, shuddering breath. There’s something else here, too. “you gonna let me in, sweetheart?” Sans brushes a soft cheek with the backs of his hard fingers, soothing and patient. “gonna show me what you need?”

Mettaton lets Sans in because they both want the same thing: to been seen, to feel heard. They want attention, given and received. They want…

Sans moans, the pleasure of what he discovers enough to surprise it out of him. Mettaton wants to give people _hope_. He wants to help them believe they’re all going to make it out of here someday, that things can and will get _better_. Because doing that for other people helps him remember how to do it himself.

Giving others hope gives _him_ hope, gives him something he can hold on to in his heart when the days are too long, when the endless nights settle around his soul like chains.

“you’re real good at this,” Sans whispers, using the hand still at Mettaton’s nape to bow his head, let Sans press his frontal bone against his forehead. His hard, flexible palm soothes the back of his neck up and down as they gaze together into Mettaton’s slowly revealing depths. “a true showman, huh?”

Mettaton can hear his breath catch when the little bloom of flattered amusement comes up so Sans can see it. Then more, and bigger, and something else floods up to the surface behind it, something neither of them can deny. It’s right there, the truth of it warming them to the core.

Mettaton waited a long time to do this, partly _because_ he wanted it so much. He wanted this: not just to be seen, but to be seen by Sans. He wants to share this with him. The floodgates are open, and Mettaton wants _more_ than just to be seen for who he really is.

He wants Sans to _know_.

“oh god,” Sans breathes. “metta…”

He wants Sans to know how he is inside, wants Sans to know how Mettaton feels about him. What this has meant, the way Sans is...he’s… Mettaton lets out a short, tight sob; he shivers almost like Sans with the strength of his desire.

“sh-sh...” Sans soothes softly, rolls his forehead against Mettaton's as phalanges trace their complex, unhurried way down his shoulder to his elbow, from his elbow to his wrist. “you sure?”

Sans already knows, but he still sees the answer.

A slim middle phalanx curves delicately into the cleft that’s at the top of Mettaton’s perfect, luminous heart.

They let out a shaky moan together as soul and bone _become_. Sans’s voice is deep and lushly complex; pleasure and surprise lend a soft chirp to Mettaton’s metallic tenor.

Sans _knows_ Mettaton, and Mettaton _feels_ Sans. Mettaton’s never done this before, but his soul is so eager that everything he feels for Sans burbles right up in an excited, clumsy rush.

He wants Sans to know that Mettaton _loves_ his terrible shows.

As much as he loves his own _,_ and that’s… that’s really saying something.

Sans knows how his own nimble phalanges gleam in a crooked yellow spotlight as he makes a crude gesture, the iridescence of what for him counts as exertion beginning to gild his frontal bone as that rich voice carries through the crowd. Sans uses the raw strength of his soul to make sure everyone can hear him, can understand the intent behind his godawful jokes, his pointless stories, the meandering notes of his trombone.

His lovely golden laugh outshines the spotlight.

He _projects_.

Sans reminds each and every person who comes to see him of the comfort that can be derived from the familiar. They pay exorbitant amounts to hear the same corny jokes yet again, to feel soothed and inspired by Sans’s willingness to get up there and do it over and over for as long as it takes.

The patience to persist until they’re all free, things get better, and change becomes possible.

The justice to see it through, to make good on his promises until good things happen for all of them someday.

Every monster underground is familiar with the way Sans has of showing up nearby just as the weight of continued existence seems more than they can bear.

He leans against the edges of the world in a flash of shadowed white, hands always hidden because they are never idle, and he’s not about to break character. Sans is the faint breath of dangerous chill appearing from nowhere. He’s a sharp grin, a saucy wink, and a low, breathy chuckle.

Because Sans is everywhere at once, no one feels like their absence would ever go unseen.

Everyone knows Sans.

Everyone knows they would be missed.

Sans and Mettaton are a lot alike: a yawning abyss of need at their core.

Sans keeps everyone at arm’s length, then showers them indiscriminately with what he wants most: to feel seen and heard, to feel accounted for, to know someone tried to make the day a little brighter, however long it lasts.

Mettaton pulls everyone into his world with him, then showers them indiscriminately with what he wants most: compliments and admiration, to be greeted like he’s someone important, to feel like his presence makes a difference.

They are all very different.

They’re a lot alike.

Mettaton’s managing to calm himself now, breathing evenly as the flood of emotions evens out. He sighs, then opens his eyes. Leans up to kiss Sans’s face softly with a little mewl.

“got a question,” Sans rumbles softly. “right now i’m jus’ letting you get used to it, but uh. was wondering if i could make you feel good?”

Mettaton’s surprised by that, because he already feels remarkably good. But if there’s something even better, he’s definitely…interested? …in that?

“lemme know if you like this,” Sans murmurs. He nuzzles at Mettaton’s narrow jawline and

_\--a shiny pink boot parts a slit in the curtain; the raucous applause as Mettaton appears, throwing the boot aside to lift his long, slinky arms and soak in the noise, is muted by the secret twinge of excitement in Sans’s soul, the way his magic agitates just thinking about what might happen later but oh,_ stars _, this is already more than enough--_

Mettaton gasps. Oh my _goodness_. He wasn’t expecting something like _that_. He’s panting again; he feels Sans’s excitement at his arrival in a way that can’t be doubted, can’t be dismissed. Feeling the effect he always hopes he could have, to bring that bright little spark of anticipation into peoples’ lives. Into someone’s life.

Into Sans’s life.

Sans lets him feel his sincere admiration: Mettaton’s commitment to fighting the fundamental aimlessness of their existence is something Sans has always been drawn to.

“that okay?” Sans breathes, letting the feeling fade. “lemme know...”

Mettaton definitely likes it. He closes his eyes, ready for whatever else Sans has up his sleeve.

“heh… ‘m kinda sans sleeves at the moment, but how bout-”

Sans gives Mettaton a little tour of the many ways he’s made Sans feel, private and public. Things that reminded him of Mettaton, things Mettaton reminded him of. He rolls him under with the slow warmth of camaraderie and comfort he’s found in his presence, the way he looked forward to performing with Mettaton when he couldn’t muster up the motivation to go it alone.

They both crave something to hold on to; a physical connection to ground the intensity of the metaphysical sensations they’re sharing.

Sans lets Mettaton take hold of his pelvis again, encourages him to guide the tight seam of Sans’s pubis back and forth on his cock. He uses both hand to guide him, shuddering as Sans’s touch intensifies without his own buffering touch alongside. Mettaton didn’t know that would happen, but it turns out he’s very much into it.

Sans grunts contentedly with the easy, simple pleasure in his body, a bone arm slung up around the back of Mettaton’s neck, the other hand holding Mettaton’s soul just under their faces. His bones mist with sweetness once more to make for a smooth glide; Sans shudders and sighs as he’s moved more quickly, and another freshet of his magic slicks them both anew.

Sans takes a few shaky breaths to gets used to so much at once, then tentatively shares a flicker of an emotion happening _now_ : a shaky new tendril of something warm-satisfying-surprising. Like giving someone a gift, or when you can tell they’re happy to see you.

“you like that?” he murmurs.

Mettaton’s thumb strokes Sans’s sacrum gently; Sans knows a thread of curiosity that offers interest rather than demanding answers. Sans nuzzles Mettaton’s face while he thinks about it.

“didn’t know i could make someone feel good this way,” Sans says breathily, curving his spine to tilt his pelvis indicatively. Mettaton feels that movement as a wave of pleasure through his entire body, so Sans does it again.

Mettaton doesn’t know why Sans wouldn’t let anyone else touch bodies with him this way, but he sure is glad Sans is sharing it with him right now. A short little huff leaves Sans’s nasal aperture. “can’t let or not let anything if no one wants to in the first place. no one… who had something like you got, anyhow.”

Sans is hesitant, but Mettaton feels so… stars, it’s like they’re sliding down the greased pole of how much they want this together. Makes Sans want to share himself, see what Mettaton thinks and feels about it. God. Sans wants to make him feel as amazing as Sans does, and he plans to.

Sans can’t explain it, so he lets him feel it: Sans’s partners mostly just wanted his hands, and Sans was happy to offer them. Their bodies tangle closer, shared introspection making their movements vague and intermittent. Phalanges spread wide as Sans’s breath goes ragged; Sans wanted them to feel pleasure, because Sans is… he wants to be of _use_. He wants to have something to offer someone, because he…Sans can’t…

Sans’s depths grow murky, revealing their existence by obscuring themselves. He waits for a long moment, steadies his breathing. This is less an emotion Sans feels, drifting closer to what it feels like to _be_ Sans. A deeper kind of intimacy. He eases back from it in favor of perspective, letting Mettaton gain a better understanding of what it is if he can.

The sharpness of Mettaton’s interest surprises a soft moan out of Sans; he slows his movements, holds him closer. Sans tilts his skull, traces his nasal bone delicately along Mettaton’s soft features as he exhales raggedly.

Sans doesn’t offer up his depths, but he lets Mettaton feel the coolness that heralds them, like a suddenly frigid current come to pluck at a basking swimmer’s toes. He hesitates when Mettaton gasps, then slowly comes back when he softens and relaxes into it. Just that little hint, letting him feel how

[more (he [Sans exists] exists) exists].

Mettaton savors the novel sensation: a mood, a temperature, an experience of deliciously not-alone. He _likes_ this.

He wants _more_ , darling.

A low, breathy sound purrs out between Sans’s teeth, and Mettaton likes that, too. Sans’s body trembles and stills, his attention and desire drawn implacably by frost-edged pleasure: Mettaton’s deepening awareness of who Sans is underneath everything. A half-imagined encounter with something unknowably vast, a delicious hint of chill. Sans’s pointed fingertips dip and flick inside him: whispers of endless darkness, relentless pressure.

Their faces press tight together; wet with magic, eyes and sockets closed against the hot, humid breaths they share eagerly. Mettaton relaxes into Sans even more, everything he is grown soft and receptive and wanting. Drawing at Sans, yearning towards his core. Sans hears his own hitching breath as he tries to hold back, but… stars, Mettaton’s so _open_ for him. Sans grunts and shudders violently as temptation sparks bright; he gives in, swallows it down.

Sans allows a deeper lust to guide his touch, lets himself have a little more.

The distal tips of his phalanges curl inward, joints flexing bit by bit until a loose bone claw bends at the carpals to draw back in a careful, implacable _pull._ Mettaton lets out a breathy, surprised moan as Sans gently opens him with his fingers; what follows right behind them is a feeling of _closeness_ , a proximity-pressure that’s increasingly _Sans_.

Sans moans like all the air’s being pushed out of him, filling Mettaton’s essential self with his presence until he feels resistance, and Mettaton lets out a tight-chirped mewl.

Sans makes a soothing croon absently; his attention’s focused on communication through his touch, on letting him feel how good this is for Sans while he eases away, lets Mettaton adjust. He shares the being-held feeling, the sensation Sans experiences as _so close_ , enveloped-alongside-inside Mettaton more than bodies can achieve. Furry black lashes flicker-brush gently against iridescent bone, come to rest on silvery cheeks. Sans hiccups softly as Mettaton’s tongue darts out to taste his bones, huffs in surprise when Mettaton lets him know how sweet Sans’s pleasure tastes.

Sans isn’t even grinding against Mettaton’s genitalia anymore, utterly transfixed by the soft pressure of the soul fluttering around his touch. His pelvis presses in to slowly still Mettaton's twitching hips, locking their bodies together as another slow-shuddering, needy growl emerges from his skull. Sans nuzzles hungrily against his face, his bone arm around Mettaton tightening inevitably when Mettaton lets him know his desire is increasing rather than abating.

“me too,” Sans admits in a low, throaty whisper. “wanna feel it again?”

He does, more than he expected.

There are many ways to express or incite emotion and sensation by touching someone; this is something slightly different than either. What Mettaton’s flirting with now is who Sans is at his core, his _raw_ self. Even as full of Sans’s presence as he is, there’s so much more to Sans than this. He lets Mettaton feel that hint of chill once more, the wracking shudder he expected absorbed by the tight bone circle of his arm, held steady under his broad, heavy pelvis.

Sans moans, his spine loosening until his skull flops gently against Mettaton’s shoulder. Mettaton’s rising awareness of how much more there _is_ of Sans rolls through them both like a six-foot breaker, the pleasure effervescent and utterly engulfing.

“mm…yeah. thass _me_. you like it?” Sans is already panting. Mettaton’s skin pushes the heat of his own breath back against him, and he grinds his face into yielding softness to feel the impenetrable steel underneath. Sans’s breath huffs out sharp at Mettaton’s response: he opens toward Sans hesitantly, decadently quivering like a tender pearl of caviar between Sans’s teeth.

“oh _fuck_ ,” Sans chokes out, fingers perfectly steady despite the turbulent kinetic energy shivering its way out of him. He wasn’t expecting that. Mettaton’s eyes slide shut again; his head lolls back against the baroque hardpaper headboard. He likes what’s happening, wants _more_...but he doesn’t know exactly, um. He doesn’t know _how_ to do what Sans needs from him, in order to do whatever it is that’s got Sans so excited. Sans tries to steady his breathing, to let his natural patience temper his need.

“i’d take care of it,” Sans whispers, words tumbling out shaky and eager despite him. “all you gotta do is let me in. you want me to show you?”

He does.

Sans uses his fingers to show Mettaton what he means, each slender phalanx a bridge between an idea, a movement, a promise, and another idea.

“you’re doin’ real good,” Sans pants, “lemme hold you, k?”

Mettaton relaxes, feels a guiding touch almost like hands over his own; it’s easy to melt into the suggestion they’re making. Sans exhales raggedly as the sensation of Mettaton’s guided yielding courses through him like hot, thick syrup. Then he waits, trying to calm down a minute before doing or saying anything else.

“yeah…jus’ like that,” he manages eventually. “‘m gonna do it easy, you—o-oh _h_ h-” Mettaton does it again without being guided, and a little of whatever this edge-of-danger feeling is slips into him as easily as the broken sound Sans makes slips into his ears.

“... _fuck_ ,” Sans pants, but Mettaton can hear the smile in his voice. “always got a surprise for me, huh?” He sends a flood of reassurance to dilute Mettaton’s little twinge of worry. “nah, you’re jus’ real good at this.” Sans nudges his face into Mettaton’s neck, guides with his touch once more. “wanna do it slow? lemme feel it?”

They do it together; Sans lets how this feels for him flow steadily through his touch, leaving them both panting this time.

“… _there_ you go.” Sans’s breath hitches in anticipation, the tips of his clawed fingers moving apart to help Mettaton make room for this. For _him._ Just in case he can take it, in case he wants…. Oh, _stars._ Not all the way or anything; just enough for him to catch a little taste.

Specific kinds of touches are much less intense than general ones; this is Sans at his most raw. It’s the primal intimacy of Sans’s “I exist”, and Sans knows his soul’s stronger than most monsters. For them, doing this kind of touch with Sans… it can be a _lot_. Mettaton picks up on a coiling quirk of caution-turns-to-guilt from Sans, so he makes him know the quivery-melting desire Mettaton’s _very_ focused on satiating. Demanding as it expands; it’s not passive.

“you got me losin’ my _mind_ here, metta...” It’s a tight whisper, neither of them quite sure if it’s a warning or a plea.

Another merciless wave of desire from Mettaton, and Sans lets out a low, hoarse moan. He never imagined Mettaton would want _this_ with him, that he’d be so pliant and adamant at once. Sans had planned to help Mettaton feel whatever he liked best, never imagined what he wanted to feel was _Sans_. Just thinking about it makes Sans’s bones shake hard enough to rattle; he tries holding his breath. Not too much; not too much.

Then Mettaton slides his hands up Sans’s back and curls his fingers right into the spaces between his ribs. Pulls in to brush his spine _just_ how he likes it best. They moan helplessly together at how good that blunt heat pushing _inside_ feels, the surprised sensation rolling right out of Sans and into Mettaton. It hits him hard, sloshes around and comes right back into Sans three times bigger than it left. What pours back into Mettaton then is a messy fraction of just how much Sans _wants_ _(??)_ , so strong that Mettaton feels that strangled desperation tear itself out of his own throat in ascending, glitching beeps.

“j-jus’ a lil bit…” Sans chokes in capitulation, utterly lost.

That frozen hurricane approaches in increments, a tempest held carefully in a teacup of delicate bones. The current grips the edge where Mettaton begins, and they gasp in unison as it tightens. Mettaton cries out as he skirts the raw power that allows Sans to exist, the chaotic depths of the calm-surfaced, restless ocean that _is him._

Sans is a swirling crucible laced with bioluminescent sparks of patience and temptation, sharp points of lust and pain glinting far, _far_ below. Gravity reverses itself; Mettaton’s dangled helplessly above what’s suddenly the sky, something neither of them have ever seen.

It doesn’t matter. Nothing else exists anymore; only _this_. Only them.

Sans’s breath hitches as he struggles for control, but he’s… oh, _stars_. He’s melting right down into this spreading-watercolor embrace and it feels _so fucking good_ , he’s...he can’t help himself. His truth is spilling over, desperate to speak itself into being. His phalanges tighten into individual hooks to hold everything steady, to create limits for the flash flood they’re caught up in together.

Sans feels an exquisite, fluttering pressure as Mettaton once again takes as much of Sans’s presence as he can hold. Mettaton breathes shallowly, broken whimpers falling out of him as his hands loosen and slide away, then return to absently scrabble at unforgiving bone. His body succumbs to the touch in his soul, hands finally coming to rest on Sans’s ilium.

Mettaton feels like he’s flying without weightlessness, a thrillingly corporeal and breathless orbit around the physical anchor deep inside him. He feels exhilarated; then he tumbles right apart into the seething surf as he’s kept so very, perfectly safe. Everything that makes him who he is accounted for, cherished, gift-wrapped, and touched fondly as it dissolves away into the impossible, roiling ocean of _Sans_.

He can’t bear it; he _loves_ it.

The bones surrounding and supporting him press trembling-tight, thrumming with deceptive stillness. Their mouths steal each others’ breath greedily; Sans is barely aware of the magic spending jubilantly out of him with each pulse of sensation in the soul in his hand. He flows iridescent at sockets and joints, sliding thickly down Mettaton’s cock where it’s pinned under his pubis.

Mettaton gasps wetly under the torrent of Sans’s desire, body limp and breathless inside the supportive cage of Sans, soul seething tight around bone. Sans bends his wrist back once more with a strangled groan.

Sans is the cliff past which there is nothing. He begins where time ends.

So careful as the chaos inside him bulges inward, a storm boiling up on the horizon that no one will escape.

So gentle as it scours them bare together, clinging like starving lovers at the absolute end of everything.

“jus’ a lil more,” Sans begs rawly, “lemme jus’--o- _oh_ fuck, _please--_ ”

 

and time stops because

_::Mettaton feels Sans::_

the infinite impression of everything he is, was, and potentially could be at once. It’s nothing more than a touch, no more than souls straining toward each other through the thin membrane of Sans’s body. His blunt-pointed bones buried in Mettaton’s luminous heart become the only thing that exists. It’s _everything_.

 

All Sans has ever known is the soft-open tremble around his impaling fingers the instant they brush Mettaton’s quivering, pinioned soul with the howling charybdis at his core.

 

Mettaton is senseless in the ecstasy of an eternal moment; doesn’t hear his own broken cry as he balances on the edge of being taken. But Sans does, even over the astonished wail of completion ringing through his own skull. This isn’t dangerous, but the sheer strength of Sans’s essential self, even felt through the protective buffer of his body, is obviously an overwhelming sensation for Mettaton.

It had only been a fraction of a second, more than enough to allow Sans one of the most intensely pleasurable experiences he’s capable of. Sans is equal parts sheepish and grateful, but he only lets Mettaton feel the latter as he eases back, phalanges straightening carefully.

Sans sobs for breath as he comes down, tries to calm himself as he floats Mettaton carefully away from the riptide and back to the shallows, a sun-warmed rind that’s just as important and real as what’s inside it. He pets his hair gently with his other hand, making soft, clumsy crooning noises to ground him, rather than withdrawing too quickly and disorienting him all over again.

“’m right here, okay?” Sans manages in a shaky rumble. “i gotcha.”

Mettaton still flounders, a little out of it after something he, he definitely wanted and was satisfied by, but he’s a little….but… but did _Sans_ like it, too? Is he okay?

“sh-sh-shh,” Sans soothes; they’re still sort of mirroring the feeling-knowing bleeding back and forth into each other. He nuzzles Mettaton’s face and spreads his fingers apart, rub-shaking side to side to dissipate the intensity of his presence more quickly.

“s’okay, sweetheart. you made me feel _real_ good, alright? you felt _so_ …” Sans’s voice chokes off around a lump of emotion, dissolves out into a shuddering breath. Mettaton lets out a faint moan as he feels what he means, how true it is.

Sans tucks his skull between Mettaton’s neck and shoulder, muffling a sniff or two as he closes back in around the turbulence inside him. Mettaton tilts his head to rest his cheek on Sans’s parietal bone, sighing as his eyes flutter shut. They stay like that for quite a while, Sans carefully soothing and calming, touching and whispering until everyone can tell who’s who again.

Mettaton’s feeling a bit tempest-tost, maybe _oh_ -so-slightly shipwrecked, but… Sans pulls back to look at his face, and Mettaton’s eyes flutter open and focus. They both smile, noticing they’re about as wet as if that were literal.

“you okay?” Sans asks sheepishly. “didn’t uh, didn’t really set out to-”

Mettaton’s offense interrupts him; he must have showed his feelings on his face as hard as he was trying to keep it out of his touch. The offense softens, because Mettaton’s pretty familiar with feeling a strange guilt after getting something you want as much as Sans had wanted that. He just needs Sans to understand that Mettaton wanted it just as much.

The soft white points in Sans’s sockets drop, but only to the soul in his fingers. A moment of silence, then he lets him feel this: a complicated tangle of feelings like he took too much, didn’t give enough. That it was too intense for a first touch, that he--

He knows a tart flash of pique; Mettaton had deepthroated Sans’s tailbone until he passed _out_ , for fuck’s sake. Apparently they _both_ like extremes. It’s actually remarkably convenient if Sans would stop being so--

Sans’s eyes glint like diamonds as he raises them to meet silver ones; Mettaton’s thoughts freeze under a fraction of what that tailbone thing had felt like for Sans. Revenge is swift if unintentional; Sans isn’t pinning Mettaton’s hips anymore, and his body responds to the burst of unexpected sensation by sliding his cock along the thrumming crux of Sans’s pubic bones.

“mmm…not the worst idea you’ve had,” Sans says, managing to smile through the dazed expression in his eyes. Sans takes over, moving in ways he’s figuring out please Mettaton the most. After something that intense, Mettaton’s body craves release.

In more than one way, and it turns out his soul wants something, too. They smile together at the warm, spreading anticipation every monster knows and feels. Mettaton wants to push his magic out, wants to feel it go inside. Much the same as Sans doesn’t allow monsters to push their magic into his soul, Sans doesn’t push his own magic in theirs, either.

But Sans manages to find his balance without pausing his movements, scrabbling for Mettaton’s hands one by one and bringing them up so he can push his own magic. Sans twines all of their fingers together carefully, sockets narrowing around his expanding eyes as he pulls away for a long beat, then slides all twenty fingertips in at once. They shudder and writhe slowly together at the strength of their connection, a ragged exhale heralding the sweet plateau of pleasure expanding between them to support and prolong the moment.

“yeah,” Sans rambles encouragingly, skull falling back with bliss as Mettaton’s magic seethes in. It’s a tight, electric tingle around Sans’s slim fingers, buried deep in his essential self. The slow circling of his pelvis doesn’t stop as Sans prods a tiny distal fingertip along a spot Mettaton's magic becomes not-him, one of the important elements Alphys had built into his skin.

Mettaton’s magic sparks and shivers like bright citrus as it spreads away, pushing deep into Mettaton’s essential self as what they’re sharing together becomes part of him forever. Sans keeps touching, agitating the magic around in his soul, pushing back against it to heighten their pleasure, to savor it coming out around his fingers. Sans’s idly toying fingertips enhance the sensations to decadent peaks and quivering edges. Their bodies slow to draw out Sans’s participation in Mettaton’s act of self-love.

“ohh…” Sans moans, “ _there_ you go, sweetheart,” urging him closer to the edge with unhurried but insistent glide of his pelvis. This is the moment Mettaton wants to carry with him, to push into himself with his magic and make it last as long as possible. Their shared _now_ is an endless silver-lit valley between the profound satisfaction and overwhelming sensations Sans had put inside him, and the slowly growing urgency his body feels to orgasm.

Then there’s a soul-deep sigh, a hint of static crackling through its length. Mettaton’s both satisfied and ready, so he guides his soul back towards himself, into itself. He lets out a glitchtone cry as his soft glow disperses, arching up tight as he feels Sans’s touch spreading through him along with his own pushed magic.

Mettaton leans in, touches his forehead to Sans’s frontal bone and hugs him close for a long, breathless moment as they share his rush. He kisses along Sans’s mandible sweetly before leaning back to watch Sans riding him together. Hot fingers fervently roam his bones as Mettaton’s climax approaches.

“I’m close,” Mettaton pants, and Sans lets out a low, eager purr.

“yeah? gonna come for me?” Mettaton’s broken little affirmative hits him right in the base of his spine. “this getting you there? you need me to-”

“Please don’t stop,” Mettaton hiccups, wrapping his arms around Sans tight again and thrusting up against him. “Yesss, perfect,” he pants into hard, complex bone. “Just like t-this...”

Sans is thrilled at the chance to get exactly what he wants with nearly zero effort on his part. He glories in Mettaton’s urgency, his breathy-beepy moans, his thighs trembling between Sans’s femurs. He lets the bones of his hands tangle into soft black hair, lets his skull fall back as that hot mouth ducks down to find his vertebrae. It’s just as easy and overwhelming, as frightening and beautiful to give himself up to the physicality of this as it had been for Mettaton to take Sans. Mettaton’s making it happen; Sans just has to let him, and the pleasure and movement and closeness shake his thoughts loose from their moorings to drift away into the ether.

Mettaton falters as he tips over the edge. Sans takes over the rhythm; each slide of his thrumming pubic symphysis against Mettaton’s twitching cock drawing pearly fluid to trail gently over the panel on his belly. But of course Mettaton has one last plot twist for him. Instead of stopping, he holds Sans even tighter and lurches up to his knees, making Sans squawk in surprise as he wraps his bone legs tight around him with a clatter.

He sucks in a breath for a mild objection. Then Mettaton lies Sans down gently on his back like Sans is something special, like he’s important and valuable, and Sans finally sees the expression on Mettaton’s face.

Sans reaches up and pulls Mettaton down on top of him with a ragged, vulnerable noise.

Sans thought it was overwhelming before, but it turns out, uh. That needs revision. His phalanges are back in Mettaton’s mouth, and Mettaton’s still sliding his cock against Sans slow and insistent, or fast and flickering, or light and teasing. They’re slicked below and between with Sans’s magic as Mettaton’s earlier spend drips down into his ribcage and the space Sans doesn’t have a belly to patter at his spine. Or maybe that’s his too; he can barely tell anymore.

Mettaton only pulls Sans’s fingers from that saucy mouth once in a while to whisper awful-sweet, candyglass shards of nothing against his skull; to lap Sans’s dulcet delight from trembling hardness; to double over and set his teeth recklessly against vertebrae; to growl his glitchtone lust against bone until Sans voices it for him like an instrument. Mettaton’s hands roam with devouring care, as busy as his mouth, his cock. Blunt heat pushes into all the tight places that Sans likes best until he’s pretty sure he doesn’t have a mind anymore. And that’s for the best, because all Sans wants for gyftmas is to be this chubby, bony, moaning little ball of _doing this_ forever. And hey, now he knows his obturator foramina can make convenient, extraordinarily sensitive handles. Who knew.

Sans starts to feel hot and used between his legs, polished carefully over and over like something Mettaton plans to keep; we’re talking a _high gloss_ kinda shine. Sans makes what might have been a laugh if it wasn’t actually a moan, imagining his own gleaming, buffed pelvis as a trophy on Mettaton’s mantle in one of those videos where he pretends to smoke a bubble pipe. The permeable magic that holds his pelvis together feels hot too, heavy and loose in the best possible way. Sans lets his skull fall to the side, sockets half-mast, eyes unseeing as he lets an arm dangle over Mettaton’s shoulders, the other just lying there bent and faintly twitching on the rumpled duvet.

When Mettaton eventually comes again, all the robot manages is a dazed grunt huffed right down inside Sans’s ribcage from the top. The soft sound disappears under Sans’s voice pealing like a struck bell, sympathetic cries torn out of him with each thrust, the wet heat of Mettaton’s climax a stop-motion, inevitable tide.

Sans’s voice shakes apart to become a long ragged breath when Mettaton's pleasure-maddened tongue finds the spot Sans’s mandible’s fused on the right side. It slips right in and keeps going until his _between_ narrows to solid bone in a thin little slit. Sans’s eyes wink out as he huffs in ecstatic shock; his body falls limp.

Mettaton’s spent magic pours down through Sans’s filigree body to soak the mattress.

 

Some time later, Sans finds himself lying on his front, skull resting on his crossed arms and watching Mettaton laughing at one of his favorite bad jokes. He’s about ten inches away, in much the same position.

Every once in a while Sans flops over so Mettaton can feed him one of the cardboard coasters he had made special just for the new hotel, then rolls back to set up another lengthy joke. He wonders if this is how Mettaton feels when he pretends to be a box and lets people put money in his head. Even if it’s not, Sans can’t imagine it could feel any better than this does.

Heh. Sans feels pretty happy, actually. Weird.

 

“don’t gotta tell me or anything, but uh.” Sans touches Mettaton’s shoulder lightly. “you like this one?” The slimmer, smaller body. The enhanced genitalia, the facial features narrow and fine.

Mettaton’s gaze goes distant. Just when Sans is about to change the subject, he speaks.

“I don’t know if I’ll ever be able to just...leave it how it is.” Mettaton’s eyes are shadowed by his hair, and he looks blank for another long beat of silence. That wasn’t what Sans asked, but he’s happy to listen to whatever Metta feels like saying. “It seems like…every time, there’s something. It’s like…something’s wrong with me.” That tinny voice goes faint, vaguely ashamed. “I always end up eventually wanting it to be different.”

Sans doesn’t touch him, doesn’t impose. He just makes his throatclearing noise again before speaking.

“doesn’t really matter what i think, but uh. seems to me there’s nothing wrong with wanting to change it up a little?”

Mettaton quirk a perfect black brow at him silently. Sans shrugs, glances away.

“nothin’ wrong with being happy with how your body already is, right? even if you don’t like everything about it?”

“Of _course_ not,” Mettaton blusters, privately stung, but Sans shakes his head adamantly.

“ _no_ , no… it’s not…i meant, if there’s nothing wrong with feeling like _that_ , seems like there’s nothing wrong with being okay with it _changing_ , either?” Sans sighs; that’s what he gets for trying to speak from his soul.

“’m saying this all wrong. ‘m sorry. i jus’ meant like, my body doesn’t change, right? and yeah, i don’t like everything ‘bout it. don’t love it, don’t…hate it. but i’m okay with it, most a the time.” He sighs again. Sincerity’s always been the ruin of him. That and Mettaton’s mouth. Hopefully he won’t have to kiss it goodbye forever after putting his foot right in his own. Sans can let just about anything go…but he doesn’t always _want_ to.

“so if i’m okay with _not_ changing…why’s it bad if _you’re_ okay _with_ changing? maybe nothin’s _wrong_ with you at all. maybe you’re not… trying to get rid a what you got, more like you just wanna… keep moving? like you wanna always be becoming, instead of ‘ending up’.” Sans rasps a tear out of the groove beneath his socket with his thumb. Wipes it on the bed and pretends he didn’t. “cause we don’t really _ever_ end up. we’re always changing, no matter what.”

Geez. Well, that was a lot more than he really intended on saying. Sans seethes iridescent across his skull, looks apologetically at Mettaton before readying a joke to lighten the mood. Then he stops, because those silver features are soft with wonder.

“I never thought of it like that before,” that sweet, tinny voice muses softly. “And it’s true. I’m happy with my body right now, but… I still want to change it.” Then the shadow returns, and he sighs. “But I don’t think I could ever really convince Alphys I’m not unhappy with her work. What an odd little monster she is. Half the time when I make a suggestion, she seems crestfallen… then half the time she seems delighted?”

Sans shakes his head. “alphie’s the sort to take that kinda thing personally. i think she figures you needing her to work on it might be the only thing keepin’ ya around, though.” He surreptitiously looks to see if Mettaton can take the hint, but he doesn’t think so. Oh well. Plenty of time to work up to that.

“How ridiculous,” Mettaton remarks lightly. “Of course I owe her everything. She knows that.”

Sans is pretty sure she doesn’t, but that’s none of his business.

Mettaton lies on his side, hand tucked under his face and staring dreamily at something behind Sans’s head.

“Why settle for anything, if you don’t have to?” he whispers vaguely.

“i dunno….i’m kinda the epitome of settling for stuff,” Sans points out shamelessly.

“Like wearing the same clothes every day?” Mettaton giggles.

“heh heh heh...yeah. speakin’ a which. any luck finding my bro yet?” Sans feels one of his sockets slide shut, lets his grin sharpen with mischief. Papyrus is as hard to pin down as Sans is omnipresent; you can only find him where he _wants_ to be found. Which is generally when he’s good and ready.

(Sans never _doesn’t_ know _exactly_ where Papyrus is, but only if he bothers to think about it. Right now Papyrus is running along the cavern roof high above Snowdin, chasing after Annoying Dog and trying to retrieve Undyne’s box of skinny cookie things she was saving to give Alphys later.)

Mettaton pouts prettily. “You know…for someone who claims to be my biggest fan, he has a rather slippery way of never being where _I_ am at any given time. The underground is not that _big_ , darling.”

Sans tightens his arms to hide the lower half of his face, does his best to suppress the giggles.

“eh, i dunno. think he’s jus’ intimidated by your stardom. but once he gets brave enough…”

Mettaton gives him a suspicious look.

Sans shrugs like cardboard wouldn’t melt in his mouth.

“hey, s’no skin off _my_ bones. just thought you two would really hit it off.”

“If it wasn’t for Alphys, I’d _swear_ you’re making him up.”

Sans sighs, turns his skull until his grin becomes visible again. “mm...guess i c’n understand that. _i_ can’t believe the coolest dude in the universe is _my_ brother half the time, neither.”

Sans stretches out on his front until his hands dangle over the side of the bed. They’re all clean now after the nap/bath Mettaton had given him. Sans shivers just thinking about hanging half-asleep and half-floating, arms slung around Mettaton’s neck to keep him from just drifting away in all those bubbles. Getting dabbed clean with a soft little cloth, catching some Z’s while Metta made a few hilariously unnecessary business calls. Hot water soothing away the almost-soreness in all his little nooks and crannies. Mettaton had given Sans quite a workout, but he’d done most of the heavy lifting, so that...works out. Heh. Nice to know Mettaton’s body is waterproof at the moment, too. Kinda gives Sans an idea.

“you ever think bout doing an escape act? one a those uhhh. water tank thingies?”

Mettaton’s definitely looking at Sans again now. He doesn’t often share ideas of his own, but something about doing it right now feels good. Gives him a warm little glow right in his soul as delighted incredulity slowly creeps over Mettaton’s features.

“Are you suggesting…a _magic show_?”

Sans snorts, sockets going long and oval. “mmhmm. human magic show.” The phrase is actually kind of a bawdy one for monsters, which makes the whole idea even better, in Sans’s opinion. “think i’d make a pretty good lovely assistant.”

Mettaton scoffs. “You just go to sleep if you’re not the center of attention! I’d end up standing there, trying to make you disappear and you’d still be snoring under the tablecloth when I picked it up!”

“…yeah,” Sans sighs in lusty agreement, slow-blinking his sockets happily. “you wanna chainsaw me in half after?”

“Of course not,” Mettaton blinks rapidly. “I’d save that for after your “ _comedy_ ”.”

“oh man,” Sans half-whispers conspiratorially. “betcha alphie could rig somethin up ta make that springloaded pudding trick work with fake blood and stuff it all in here,” Sans say, indicating his hollow-seeming middle with his thumb.

Mettaton can’t hide the intrigued look in his silvery eyes, and Sans’s soul wiggles inside him like an excited puppy.

 

There’s nothing better than having something to look forward to.

 

 

 

 

*to disambiguate: no souls were merging or anything like that. Sans was just literally touching Mettaton’s soul in a specific way. The way I write different soul sex acts and the ways they can be combined aren’t inherently “more” or “going farther”. They’re actually different processes and sensations.


End file.
